Question 1

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): Leguminous plants help to revive and improve soil fertility. Reason (R): Microorganisms present in the root nodules of leguminous plants f…

Accepted Answer

Introduction / Context: This Assertion and Reason question examines basic concepts of soil fertility and the role of leguminous plants in agriculture. It focuses on biological nitrogen fixation, a key idea in biology and environmental science. Farmers often include legumes such as peas, beans, and pulses in crop rotation to improve soil fertility, and this question asks you to connect that practice with the activity of microorganisms in the root nodules. Given Data / Assumptions: Leguminous plants are those that belong to the pea family, such as gram, peas, beans, and lentils. Assertion (A) states that legumes revive soil fertility. Reason (R) states that microbes in root nodules of legumes fix atmospheric nitrogen. We assume the standard school level explanation of nitrogen fixation in biology and agriculture. Concept / Approach: Nitrogen is an essential nutrient for plants but cannot be directly used by most plants in its gaseous form as N2. Certain bacteria can convert atmospheric nitrogen into nitrogenous compounds like nitrates and ammonium that plants can absorb through their roots. In leguminous plants, some of these nitrogen fixing bacteria, for example Rhizobium species, live in root nodules in a symbiotic relationship. This biological nitrogen fixation naturally enriches the soil with nitrogen compounds, improving fertility without chemical fertilisers. Step-by-Step Solution: Step 1: Consider Assertion (A). In practice, farmers often grow legumes in crop rotation, and scientific studies show that legumes can improve nitrogen content in soil. Therefore Assertion (A) is true. Step 2: Reason (R) states that microbes in root nodules of legumes fix atmospheric nitrogen. This is a well known fact. Bacteria like Rhizobium infect legume roots, form nodules, and convert nitrogen gas into compounds that the plant can use. Step 3: These nitrogenous compounds not only nourish the legume plant but also remain in the soil as part of organic matter or as leftover nitrates, thereby enriching the soil for subsequent crops. Step 4: Because of this biological nitrogen fixation, the soil where legumes have grown becomes more fertile compared to fields without such crops, especially in terms of nitrogen availability. Step 5: Therefore Reason (R) is true and provides the direct scientific explanation for why Assertion (A) is correct. Verification / Alternative check: Agriculture and biology textbooks repeatedly highlight crop rotation with legumes as an eco friendly way to maintain or improve soil fertility. They show diagrams of legume roots with nodules and explain how nitrogen fixing bacteria live there. These explanations explicitly connect the presence of root nodules and nitrogen fixation with improved soil fertility. This independent confirmation supports both the truth of Assertion (A) and the explanatory role of Reason (R). Why Other Options Are Wrong: Options that state that Assertion (A) is false contradict well established agricultural practice. Options that deny the truth of Reason (R) conflict with standard microbiology facts. The option claiming both are true but R does not explain A is also incorrect because nitrogen fixation is exactly the reason legumes enrich the soil. Common Pitfalls: A typical mistake is to think that only chemical fertilisers can improve soil fertility and to ignore natural processes like symbiotic nitrogen fixation. Another pitfall is confusing nitrogen fixation by bacteria with nitrogen absorption by plant roots. In this question, the microorganisms in root nodules are the key players that convert atmospheric nitrogen into plant usable forms. Final Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A), so the correct option is Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).

Question 2

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): The people of the Indus Valley Civilization knew the art of navigation and sea travel. Reason (R): Many Indus Valley seals and archaeologi…

Accepted Answer

Introduction / Context: This Assertion and Reason question is from ancient Indian history and archaeology. It focuses on the Indus Valley Civilization, also known as the Harappan Civilization, and asks about the people s knowledge of navigation. The Reason points to archaeological evidence such as seals and artefacts. You are expected to know both the nature of Indus Valley trade and how historians draw conclusions from material evidence. Given Data / Assumptions: The Indus Valley Civilization flourished in north western parts of the Indian subcontinent. Assertion (A) states that Indus Valley people knew the art of navigation. Reason (R) states that Indus Valley seals indicate overseas trade. Archaeological sites like Lothal show dock like structures and evidence of maritime activity. Concept / Approach: To evaluate the statements, we first check whether the Indus Valley people actually engaged in sea trade. Historical and archaeological evidence include seals, dockyards, and trade goods that reached distant regions such as Mesopotamia. If such long distance trade took place across seas, then at least some Indus Valley merchants must have known navigation and sea travel. Thus, overseas trade evidence can serve as a strong reason to infer navigational knowledge. Step-by-Step Solution: Step 1: Archaeological excavations at Indus Valley sites such as Lothal in present day Gujarat have revealed structures interpreted as dockyards or ports. Step 2: Indus seals and beads have been found in regions far away, including areas identified with ancient Mesopotamia. This suggests active trade links beyond the Indian subcontinent. Step 3: For goods and merchants to travel over sea routes in ancient times, some level of knowledge of navigation and ship handling would have been necessary. Step 4: Therefore Assertion (A), that Indus Valley people knew navigation, is considered true in standard historical interpretations based on the available evidence. Step 5: Reason (R) states that Indus Valley seals indicate prevalence of overseas trade. This is also accepted as true, because seals have been discovered at foreign sites and show symbols that likely served administrative or commercial purposes. Step 6: The evidence of overseas trade supports the conclusion that people who conducted this trade required navigational knowledge. Thus Reason (R) offers a logical explanation for Assertion (A). Verification / Alternative check: History textbooks often emphasise maritime trade of the Indus Valley Civilization and specifically mention Lothal as an important port town. Seal finds in Mesopotamian contexts and references to a land called Meluhha in Mesopotamian texts are used to support this view. These multiple lines of evidence align well with both the Assertion and the Reason and show that the Reason helps us infer the truth of the Assertion. Why Other Options Are Wrong: Options suggesting that both statements are false are inconsistent with widely accepted archaeological interpretations. Options claiming that only one of the two statements is true do not reflect the standard evidence based view. Saying that Reason (R) does not explain Assertion (A) is also incorrect, because the very fact of overseas trade directly implies the need for navigation skills. Common Pitfalls: Some learners may confuse certainty with evidence based inference, thinking that because we do not have direct written manuals on navigation from Indus times, we cannot say they knew navigation. In history, especially ancient history, indirect evidence such as trade goods and port structures is often the main basis for such conclusions. Final Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A), so the correct option is Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).

Question 3

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): Most of the Himalayan rivers are perennial and flow throughout the year. Reason (R): These rivers are fed by melting snow and glaciers in …

Accepted Answer

Introduction / Context: This Assertion and Reason item is based on Indian physical geography and river systems. It distinguishes Himalayan rivers from peninsular rivers and asks whether their perennial character is correctly explained by their source of water. Understanding why certain rivers flow throughout the year while others are seasonal is an important concept in geography, water resource planning, and environmental studies. Given Data / Assumptions: Assertion (A) states that most of the Himalayan rivers are perennial. Reason (R) states that these rivers are fed by melting snow. Perennial rivers are rivers that have water flow in all seasons of the year. Himalayan rivers include major rivers like the Ganga, Yamuna, Indus, and Brahmaputra. Concept / Approach: Himalayan rivers originate in high mountain regions where there are glaciers and permanent snowfields. Throughout the year, especially during warmer months, snow and ice melt and supply water to these rivers. In addition, they receive rainfall from monsoon systems. Because they have both glacial melt and rainfall as sources, they tend to maintain flow year round. In contrast, many peninsular rivers depend mainly on monsoon rain and may become seasonal. Step-by-Step Solution: Step 1: The Ganga, Yamuna, Brahmaputra, and Indus all arise from glaciated regions in the Himalayas. Step 2: Even outside the main monsoon season, glaciers and permanent snowfields slowly melt and provide a steady base flow of water to these rivers. Step 3: During monsoon, heavy rainfall further increases their discharge, often causing floods, but the basic flow remains even in drier seasons due to snow melt. Step 4: Because of this continuous supply, most Himalayan rivers are described as perennial, meaning they flow throughout the year. Thus Assertion (A) is true. Step 5: Reason (R) accurately states that these rivers are fed by melting snow. This is one of the main reasons for their perennial nature. Therefore Reason (R) is also true. Step 6: The presence of glaciers and snow in upper catchments is the direct physical cause that explains why these rivers do not run dry during non monsoon months. Hence Reason (R) correctly explains Assertion (A). Verification / Alternative check: Standard school geography textbooks classify Indian rivers into Himalayan and peninsular systems. They explicitly state that Himalayan rivers are perennial because they are snow fed and rain fed, while many peninsular rivers are mainly rain fed and thus seasonal. This classification and explanation match exactly with the statements in the question, confirming both their truth and the logical connection between them. Why Other Options Are Wrong: Any option describing Assertion (A) as false contradicts this well accepted classification. Options that say Reason (R) is false ignore the clear role of glacial melt in river hydrology. The option stating that both are true but R does not explain A is also incorrect because snow melt is precisely the reason these rivers remain perennial. Common Pitfalls: Learners sometimes assume that monsoon rainfall alone is sufficient to make a river perennial, overlooking the importance of glaciers and snowfields. Others may confuse the behaviour of Himalayan rivers with that of shorter, non snow fed rivers in the peninsula. Keeping the distinction clear between different river systems helps avoid such errors. Final Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A), so the correct option is Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).

Question 4

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): There is no fully successful and widely available vaccine for AIDS. Reason (R): The virus that causes AIDS shows rapid changes in its gene…

Accepted Answer

Introduction / Context: This Assertion and Reason question relates to human health, immunology, and virology. It specifically concerns AIDS, which is caused by infection with the Human Immunodeficiency Virus. The question checks whether you know about the status of vaccine development for AIDS and understand why creating such a vaccine is scientifically challenging. It is important to treat this as a conceptual question rather than as medical advice. Given Data / Assumptions: Assertion (A) states that there is no successful, widely used vaccine for AIDS. Reason (R) states that the AIDS virus changes its genetic code frequently. The virus responsible for AIDS is HIV, an RNA virus that uses reverse transcriptase. We consider the general statement that despite research, there is no standard, globally used preventive vaccine for AIDS. Concept / Approach: Viruses can mutate, that is, change their genetic material. HIV in particular has a very high mutation rate due to the error prone nature of reverse transcriptase and the presence of many viral variants, even within a single infected person. Vaccine development usually relies on having stable viral antigens so the immune system can recognise them. When the virus changes rapidly, antigens keep shifting, making it hard to design a single vaccine that works reliably across all strains and over time. Step-by-Step Solution: Step 1: Many diseases, such as measles or polio, have well established vaccines that are part of national immunisation programmes. Step 2: For AIDS, however, despite decades of intensive research, there is no globally accepted, fully successful vaccine that is routinely given to the general population for prevention. Step 3: Therefore Assertion (A) is considered true in the context of exam level general knowledge. Step 4: Reason (R) states that the AIDS virus changes its genetic code. HIV is known for its high rate of mutation and formation of many sub types and quasispecies, causing antigenic variation. Step 5: This rapid genetic change leads to frequent changes in surface proteins that would be targeted by vaccines. As a result, an immune response built against one variant may not protect effectively against another. Step 6: Therefore Reason (R) is also true and it provides a strong scientific explanation for why vaccine development for HIV and AIDS is extremely difficult. Verification / Alternative check: Scientific literature and health education materials often mention that HIV has a high mutation rate and that this is one of the main reasons for the lack of a simple, widely used preventive vaccine. While there are experimental vaccine candidates and ongoing trials, there is still no universal, standard vaccine programme for AIDS like there is for diseases such as polio or measles. This supports the truth of both statements and the causal link given in the Reason. Why Other Options Are Wrong: Options that treat the Assertion as false would imply that an effective vaccine is already widely available, which is not correct at present. Options that deny the high mutation rate of HIV contradict well known virology facts. Options claiming that the Reason does not explain the Assertion ignore the central role that viral variation plays in vaccine design challenges. Common Pitfalls: Students sometimes confuse preventive vaccines with treatment options like antiretroviral therapy, which are drugs and not vaccines. Others may have heard about vaccine research and mistakenly assume that a final product already exists for public use. It is important to separate experimental trials and partial results from a widely implemented, proven vaccine programme. Final Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A), so the correct option is Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).

Question 5

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): An increase in the concentration of carbon dioxide in the atmosphere would lead to melting of polar ice. Reason (R): A higher concentratio…

Accepted Answer

Introduction / Context: This question is about climate change and the greenhouse effect. It asks whether rising carbon dioxide levels in the atmosphere can cause melting of polar ice and whether the given Reason about increasing global temperature provides the correct explanation. Understanding this link is important for general awareness about environmental issues and is frequently tested in school science and competitive exams. Given Data / Assumptions: Assertion (A) states that an increase in carbon dioxide would melt polar ice. Reason (R) states that global temperature would rise as carbon dioxide concentration increases. Carbon dioxide is a major greenhouse gas. Polar ice refers to ice caps and glaciers in polar regions such as Antarctica and the Arctic, and high mountain glaciers. Concept / Approach: The greenhouse effect is a natural process where certain gases in the atmosphere trap heat radiated from the Earth s surface and keep the planet warm enough for life. Increasing levels of greenhouse gases, especially carbon dioxide, intensify this effect and raise global average temperature. Higher temperatures can lead to melting of ice in polar and glacial regions. Therefore, to evaluate this Assertion and Reason pair, we must connect greenhouse gas concentration, temperature rise, and ice melt. Step-by-Step Solution: Step 1: When carbon dioxide concentration in the atmosphere increases due to human activities such as burning fossil fuels and deforestation, the greenhouse effect becomes stronger. Step 2: A stronger greenhouse effect means more heat is trapped in the lower atmosphere, leading to an increase in the global average temperature. This supports Reason (R) and shows that it is true. Step 3: Higher global temperatures particularly affect cold regions. Polar ice caps and mountain glaciers are sensitive to small temperature changes. Step 4: As average temperatures rise, more ice melts during warm seasons and less ice forms during cold seasons. Over time, this leads to a net reduction in ice volume. Step 5: Therefore Assertion (A) is also true because increased carbon dioxide indirectly leads to melting of polar ice through the mechanism of global warming. Step 6: Reason (R) directly describes the first link in the chain, that is, carbon dioxide increase causes temperature rise, which in turn explains the effect on polar ice stated in the Assertion. Verification / Alternative check: Scientific reports, including those by international climate panels, show observed trends of rising atmospheric carbon dioxide, increasing global average temperatures, and significant retreat of many glaciers and polar ice regions. Satellite images and long term measurements confirm loss of ice in Greenland, Antarctica, and many mountain ranges. These independent lines of evidence support both the Assertion and the Reason and confirm that the Reason explains the Assertion. Why Other Options Are Wrong: Options that deny the truth of either the Assertion or the Reason conflict with widely accepted climate science. Saying that Reason (R) does not explain Assertion (A) ignores the clear cause and effect link between greenhouse gas driven warming and ice melt. Therefore such options cannot be correct. Common Pitfalls: Some learners may think that melting of polar ice is caused directly by pollution particles or chemical reactions rather than by temperature rise. Others may confuse local weather variability with long term climate trends. It is essential to distinguish between short term weather changes and long term climate change driven by greenhouse gases. Final Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A), so the correct option is Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).

Question 6

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): Most of the Himalayan rivers are perennial and flow throughout the year. Reason (R): They are fed by melting snow and glaciers in the Hima…

Accepted Answer

Introduction / Context: This is another version of the Himalayan rivers question that tests the same core idea in a slightly different option pattern. It asks whether the statement about Himalayan rivers being perennial is correctly explained by their being fed by melting snow in the Himalayas. Understanding this question reinforces knowledge about the sources of major Indian rivers and the difference between snow fed and rain fed rivers. Given Data / Assumptions: Assertion (A): Most Himalayan rivers are perennial and flow throughout the year. Reason (R): They receive water from melting snow and glaciers. Himalayan rivers include important rivers such as the Ganga, Yamuna, Indus, and Brahmaputra. Perennial means continuous flow in all seasons, not drying up completely. Concept / Approach: This question relies on the hydrological concept that river flow depends on its sources, such as rain, snow, and groundwater. Himalayan rivers originate in high altitude regions where glaciers store water in the form of ice and snow. Seasonal melting provides a relatively steady contribution even when rainfall is low. Because Assertion and Reason are very closely matched, we need to check both their truth and the causal relationship. Step-by-Step Solution: Step 1: Examine Assertion (A). Due to their snow fed nature and large catchment areas, Himalayan rivers typically have water throughout the year and are classified as perennial. So Assertion (A) is true. Step 2: Examine Reason (R). It states that these rivers are fed by melting snow. This is also true as many of them rise from glaciers and permanent snowfields in the Himalayas. Step 3: The presence of glaciers and snow ensures that when temperatures rise, melted water continues to feed river channels. Step 4: This continuous supply supplements rainfall and ensures that even in dry periods the rivers maintain some discharge, which gives them perennial character. Step 5: Therefore Reason (R) does more than simply state another fact. It provides the main explanation for why most Himalayan rivers are perennial. Verification / Alternative check: As discussed in the previous Himalayan rivers question, geography syllabi explicitly state that Himalayan rivers are perennial because they are both snow fed and rain fed. Diagrams in textbooks often show glaciers feeding major rivers, reinforcing the explanation given in Reason (R). No alternative factor explains the perennity as strongly as the snow fed source does. Why Other Options Are Wrong: Option stating that Reason (R) is true but Assertion (A) is false is incorrect because both statements are true according to standard geography. Option that says Assertion (A) is true but Reason (R) is false ignores the well established role of snow melt. Options claiming both are false or unrelated contradict textbook knowledge and misrepresent the strong cause and effect link. Common Pitfalls: Candidates sometimes focus only on monsoon rainfall and overlook stored water in glaciers, leading to confusion about why some rivers continue flowing in the dry season. It is helpful to recall that Himalayan rivers combine snow melt with rainfall, making their flow more reliable than purely rain fed rivers. Final Answer: Reason (R) correctly explains Assertion (A), so the correct option is Reason (R) correctly explains Assertion (A).

Question 7

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): Carbon monoxide, when inhaled in sufficient quantity, can cause death. Reason (R): Carbon monoxide combines strongly with haemoglobin in t…

Accepted Answer

Introduction / Context: This question comes from basic human physiology and environmental science. It asks about the toxic effects of carbon monoxide and the mechanism by which it can cause death. Carbon monoxide is a colourless, odourless gas produced by incomplete combustion of carbon containing fuels. Understanding its action on haemoglobin is important for public health awareness and often appears in school level science exams. Given Data / Assumptions: Assertion (A): Carbon monoxide when inhaled causes death. Reason (R): Carbon monoxide combines with haemoglobin. Haemoglobin is the oxygen carrying pigment present in red blood cells. We consider exposure to carbon monoxide at sufficiently high concentration and duration. Concept / Approach: Haemoglobin binds oxygen in the lungs and releases it in body tissues. It can also bind to other gases. Carbon monoxide has a much higher affinity for haemoglobin compared to oxygen. When a person inhales carbon monoxide, it competes with oxygen for binding sites on haemoglobin. If enough haemoglobin is occupied by carbon monoxide, the blood cannot carry adequate oxygen, leading to tissue hypoxia and possible death. Thus we need to check the truth of both statements and see whether the Reason provides the correct physiological mechanism. Step-by-Step Solution: Step 1: At low levels, carbon monoxide exposure can cause headache, dizziness, and weakness. At high levels, it can lead to unconsciousness and death. Therefore Assertion (A) that carbon monoxide when inhaled can cause death is true. Step 2: Reason (R) claims that carbon monoxide combines with haemoglobin. In reality, carbon monoxide binds to haemoglobin to form carboxyhaemoglobin. Step 3: The affinity of haemoglobin for carbon monoxide is many times greater than its affinity for oxygen. Once carbon monoxide occupies binding sites, oxygen cannot bind effectively. Step 4: As a result, even if the person breathes air that contains some oxygen, the blood cannot carry sufficient oxygen to body tissues. Step 5: This oxygen deprivation leads to damage in vital organs like the brain and heart and can cause death if exposure continues or is intense. Step 6: Thus Reason (R) is true and correctly explains the toxic effect described in Assertion (A). Verification / Alternative check: Medical and toxicology references explain carbon monoxide poisoning in exactly these terms: the gas binds to haemoglobin, forms carboxyhaemoglobin, and reduces oxygen carrying capacity of the blood. Symptoms and fatal outcomes are directly linked to the percentage of haemoglobin bound to carbon monoxide. This independent information matches the Reason and confirms that it is the explanation for the Assertion. Why Other Options Are Wrong: Any option that calls either Assertion (A) or Reason (R) false contradicts widely accepted medical knowledge. The idea that Reason (R) does not explain Assertion (A) is also incorrect, because the binding of carbon monoxide to haemoglobin is precisely the mechanism that leads to death in severe poisoning cases. Common Pitfalls: Some learners confuse carbon monoxide with carbon dioxide. Carbon dioxide at high levels can also be harmful, but the specific haemoglobin binding and carboxyhaemoglobin formation are distinctive features of carbon monoxide poisoning. Care must be taken to distinguish between these two gases. Final Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A), so the correct option is Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).

Question 8

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): In winter, a glass tumbler may crack or break if very hot water is poured into it suddenly. Reason (R): When hot water is poured into the …

Accepted Answer

Introduction / Context: This question is about thermal expansion and thermal stress in materials such as glass. It uses a common household example where a glass tumbler can crack if boiling or very hot water is poured in suddenly during cold weather. The Assertion states the observed effect, while the Reason attempts to describe which part of the glass expands first. To answer correctly, we must understand how heat flows and which surface of the glass gets heated more quickly. Given Data / Assumptions: Assertion (A): Glass tumbler breaks in winter when hot water is poured into it. Reason (R): When hot water is poured, the outer surface of glass expands. We assume the tumbler is initially cold, especially its outer surface due to winter conditions. Glass is a brittle material and does not quickly adjust to uneven expansion. Concept / Approach: When a hot liquid is poured into a cold glass, heat is transferred by conduction from the liquid to the inner surface of the glass. The inner surface warms up and tends to expand earlier than the outer surface, which remains relatively cold. This creates unequal expansion within the thickness of the glass. The resulting thermal stress can exceed the strength of the material, causing cracks. The Reason in the question claims the outer surface expands first, which contradicts the actual direction of heat flow. Step-by-Step Solution: Step 1: Consider Assertion (A). Many people have observed that thin glass tumblers may crack or shatter if very hot water is poured into them suddenly on a cold day. This is a real and common phenomenon, so Assertion (A) is true. Step 2: When hot water is poured into a cold glass, the inner surface of the glass comes into direct contact with hot water and receives heat first. Step 3: The inner surface therefore warms up, tries to expand, and experiences thermal expansion earlier than the outer surface, which is still relatively cold and contracted. Step 4: Because glass is rigid and brittle, this difference in expansion between inner and outer layers generates internal stress within the glass wall. Step 5: If the temperature difference is large and the glass is thin or flawed, the resulting stress can exceed the strength of the glass, leading to cracks or breakage. Step 6: Reason (R) states that when hot water is poured, the outer surface expands. This is incorrect: it is the inner surface that expands first. So Reason (R) is false. Verification / Alternative check: Thermal stress examples in physics textbooks often include the hot water in cold glass situation and clearly state that inner layers are heated first. They also note that special heat resistant glass, which tolerates larger temperature differences, is used in laboratory glassware and kitchenware to avoid such breakage. This supports the truth of the Assertion and the falsity of the specific Reason given. Why Other Options Are Wrong: Any option suggesting that Assertion (A) is false contradicts widely observed behaviour and textbook examples. Options that treat Reason (R) as true misrepresent the physics of heat conduction, since the side in contact with hot liquid must warm and expand first. Common Pitfalls: Learners may not consciously think about which surface is in contact with hot water and may assume both surfaces heat equally. Others may memorise the fact that glass breaks with sudden heating but not recall the correct direction of expansion. Always think about where heat enters a body first to decide which part expands earlier. Final Answer: Assertion (A) is true, but Reason (R) is false, so the correct option is Assertion (A) is true, but Reason (R) is false.

Question 9

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): Cotton is mainly grown in alluvial soils. Reason (R): Alluvial soils are very fertile and rich in plant nutrients.

Accepted Answer

Introduction / Context: This Assertion and Reason question is from Indian agriculture and soil types. It tests knowledge about the preferred soil for cotton cultivation and the general fertility of alluvial soils. You must decide whether cotton is primarily associated with alluvial soils and whether the fertility of alluvial soil is correctly described in the Reason. It is important to recall the difference between alluvial and black soils and which crops they support best. Given Data / Assumptions: Assertion (A): Cotton is grown in alluvial soils. Reason (R): Alluvial soils are very fertile. Alluvial soils are formed by deposition of silt and sediments by rivers. Black soils, also called regur soils, are found in the Deccan plateau and are often linked with cotton. Concept / Approach: Cotton requires a warm climate with moderate rainfall and a soil that can retain moisture but also has good drainage. In India, cotton is classically associated with black soils that have high clay content, good moisture retention, and are found in Maharashtra, Gujarat, and parts of Madhya Pradesh. Alluvial soils are indeed fertile and support many crops such as wheat, rice, sugarcane, and pulses, but they are not the typical textbook soil type specifically linked with cotton. Therefore we must judge Assertion and Reason separately and then examine their relationship. Step-by-Step Solution: Step 1: The Assertion claims that cotton is grown in alluvial soils. While cotton can be grown in various soils with proper irrigation and management, the classic and most suitable soil for cotton in exam oriented geography is black soil. Step 2: Black soils have properties such as high moisture retention and rich lime content that favour cotton cultivation. Hence the standard statement in many textbooks is that cotton grows best in black soils. Step 3: Therefore, as per typical school level generalisation, Assertion (A) is considered false because it suggests alluvial soils as the main or typical soil for cotton. Step 4: Now examine Reason (R). Alluvial soils, found mainly in river plains, are indeed very fertile. They contain fine particles, mineral nutrients, and often support multiple crops per year. Step 5: Since many different crops thrive on alluvial soils, the statement that alluvial soils are very fertile is true. Step 6: Thus we have Assertion (A) false and Reason (R) true, and clearly Reason (R) cannot act as a correct explanation of a false Assertion. Verification / Alternative check: Standard geography texts state that cotton is a crop of black soils of the Deccan plateau. Alluvial soils are usually associated with crops such as wheat, rice, sugarcane, and jute in the Indo Gangetic plains. This consistent pairing in exam material confirms that the Assertion in the question is not aligned with the usual teaching, whereas the description of alluvial soils as fertile is well supported. Why Other Options Are Wrong: Options that treat Assertion (A) as true ignore the strongly emphasised Black cotton soil association. Options that say Reason (R) is false contradict basic facts about alluvial soil fertility. The option that claims both are false is also wrong because the fertility of alluvial soils is a well known fact. Common Pitfalls: Some candidates may assume that because cotton can be grown in places with alluvial soils under certain conditions, the Assertion must be correct. Exam questions at this level, however, expect the recognition of the main or ideal soil type associated with the crop, not all possible conditions. Remember the standard pairing of cotton with black soil for such questions. Final Answer: Assertion (A) is false, but Reason (R) is true, so the correct option is Assertion (A) is false, but Reason (R) is true.

Question 10

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): A small gap is left between iron railway rails during laying of tracks. Reason (R): Iron and steel expand in hot summer and need space to …

Accepted Answer

Introduction / Context: This Assertion and Reason question deals with thermal expansion of solids and its practical engineering application. Railways provide a classic example in physics and engineering textbooks. Metal rails experience changes in length with temperature, and engineers must account for this by leaving gaps or using special joints. The question asks whether the reason given correctly explains why small gaps are left between iron rails. Given Data / Assumptions: Assertion (A): A gap is left between iron rails. Reason (R): Iron expands in summer. Rails are usually made of steel, an alloy based on iron. Temperature varies significantly between seasons and even within a day. Concept / Approach: All solids expand when heated and contract when cooled, though the amount can vary by material. Long metal structures such as rails, bridges, and pipelines can experience noticeable changes in length. If there is no room for expansion, compressive stresses build up and may cause buckling or damage. Hence, engineers design expansion joints or leave small gaps. In this question, we need to confirm that gaps are indeed left and that the stated expansion reason is correct and explanatory. Step-by-Step Solution: Step 1: Look at Assertion (A). Rail tracks do show visible small gaps at joints in many traditional track designs. These gaps are not accidental; they are left deliberately. Therefore Assertion (A) is true. Step 2: Reason (R) claims that iron expands in summer. Thermal expansion of metals including iron and steel is a well known physical property. When temperature increases, atomic vibrations increase and the solid expands. So Reason (R) is also true. Step 3: Rails laid in cold weather would lengthen as temperatures rise. If no gaps were left, this expansion could cause the rails to bend or buckle, creating safety hazards for trains. Step 4: By leaving small gaps between rails, engineers provide space into which each rail can expand without generating excessive compressive stress. Step 5: Thus, the Reason directly explains the purpose of the gaps mentioned in the Assertion. Without thermal expansion, such gaps would not be necessary. Verification / Alternative check: Physics and engineering textbooks often include diagrams showing rail joints with small clearances and explicitly state that these exist to allow for expansion in hot weather. Real world instances of track buckling during heat waves further confirm that temperature related expansion is a major design concern. This supports both the truth of Assertion (A) and the explanatory role of Reason (R). Why Other Options Are Wrong: Any option stating that Assertion (A) is false contradicts observations of actual rail tracks and textbook illustrations. Denying the truth of Reason (R) would go against basic principles of thermal expansion. The idea that the Reason does not explain the Assertion is also incorrect because the whole point of the gap is to accommodate expansion in hot conditions. Common Pitfalls: Some candidates may think the gaps are only for alignment or maintenance, forgetting the thermal aspect. Others may overlook that even small expansions, when accumulated over long lengths, can be significant. Always link examples in physics questions to the underlying physical law. Final Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A), so the correct option is Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).

Question 11

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): Pouring kerosene oil on stagnant pools of water helps to eradicate malaria. Reason (R): Kerosene oil is poisonous for mosquitoes and kills…

Accepted Answer

Introduction / Context: This Assertion and Reason question comes from health science and environmental control of vector borne diseases. It deals with an old method of reducing mosquito populations by pouring a thin layer of kerosene oil on stagnant water. Malaria is spread by Anopheles mosquitoes, which breed in standing water. The question asks whether using kerosene on stagnant pools is effective and whether the reason given about its effect on mosquitoes is valid. Given Data / Assumptions: Assertion (A): The pouring of kerosene oil on stagnant pools helps to eradicate malaria. Reason (R): Kerosene oil is poisonous for mosquitoes. Malaria is transmitted by mosquitoes that breed in stagnant water. Kerosene oil spreads as a thin film on the surface of water. Concept / Approach: Mosquito larvae and pupae live in water and come to the surface to breathe air through specialised structures. If the water surface is covered by an oil film, this breathing is blocked. The larvae and pupae suffocate and die, reducing the mosquito population. The method targets the immature stages, not adult mosquitoes directly. The question simplifies this by saying kerosene is poisonous for mosquitoes, which in school level understanding is treated as an acceptable explanation for their death in treated pools. Step-by-Step Solution: Step 1: Malaria control often involves preventing mosquitoes from breeding by eliminating or treating stagnant water where larvae develop. Step 2: Pouring kerosene or similar oils on stagnant pools creates a thin film that spreads over the water surface. Step 3: Mosquito larvae and pupae that live just below the surface must come up to breathe. The oil film interferes with this process. Step 4: Because they cannot breathe properly through the oil covered surface, many larvae and pupae die, breaking the life cycle of the mosquito. Step 5: With fewer mosquitoes emerging, the risk of malaria transmission drops. Thus Assertion (A) is true as a simplified statement about controlling malaria by treating breeding sites. Step 6: Reason (R) states that kerosene oil is poisonous for mosquitoes. In school level terms, killing larvae by suffocation or by oil toxicity is both understood as being harmful or poisonous. So Reason (R) is accepted as true and explains why the method works. Verification / Alternative check: Older public health campaigns and science textbooks mention kerosene or other oils as a method for mosquito control in stagnant water. They describe how blocking the surface prevents larvae from breathing, leading to death. While modern programmes may prefer other environmental approaches, the basic mechanism remains valid. This supports the truth of Assertion (A) and the explanatory nature of Reason (R), interpreted in a broad sense of being deadly or harmful to mosquitoes. Why Other Options Are Wrong: Options that claim Assertion (A) is false ignore the effectiveness of surface oil treatment in killing mosquito larvae. Options that say Reason (R) is false conflict with the concept that kerosene on the water surface is lethal to mosquitoes at their aquatic stages. The option stating that both are false is also wrong. Common Pitfalls: A subtle pitfall is to insist on a very narrow definition of poison and reject the Reason because the main mechanism is suffocation rather than chemical poisoning. At this level, the exam expects recognition that kerosene on water is harmful enough to kill mosquitoes, so describing it as poisonous is taken as an acceptable simplification. Final Answer: Reason (R) correctly explains Assertion (A), so the correct option is Reason (R) correctly explains Assertion (A).

Question 12

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): The steam engine is credited as an important invention by James Watt. Reason (R): There was a serious practical problem of removing water …

Accepted Answer

Introduction / Context: This Assertion and Reason question is drawn from the history of science and technology. It concerns the steam engine and the role of James Watt, as well as the industrial need that drove improvements in steam power. While earlier forms of steam engines existed, Watt s improvements had a large impact on the Industrial Revolution. The question asks you to connect Watt s work with the practical problem of pumping water from mines. Given Data / Assumptions: Assertion (A): The steam engine was invented by James Watt, in the sense that he is widely associated with its development. Reason (R): There was a serious problem of taking out water from flooded mines. Earlier engines like the Newcomen engine were used to pump water from mines. Watt made major improvements that increased efficiency and usefulness of steam engines. Concept / Approach: From an exam oriented perspective, James Watt is often credited with the steam engine, although historically he improved existing designs. The key is that his work made steam engines more practical and efficient. The need to pump water out of coal and metal mines was a major driver for steam engine development in Britain. So we must see whether the Reason about flooded mines gives the correct background for Watt s work on steam engines. Step-by-Step Solution: Step 1: Assertion (A) reflects the common textbook statement that James Watt invented or is the main inventor of the steam engine. For general knowledge level, learners are taught to associate Watt strongly with the steam engine, so the Assertion is treated as true in this context. Step 2: Reason (R) states that there was a problem of taking out water from flooded mines. Historically, deep coal and metal mines in Britain frequently filled with water. Step 3: This flooding limited the depth and productivity of mines, so an efficient mechanical method to pump out water was extremely valuable. Step 4: Early steam engines such as those by Newcomen were used for pumping, but they were inefficient. James Watt improved the design by introducing separate condensers and other innovations, making steam engines more efficient and useful for different industrial purposes. Step 5: The need to solve the mine flooding problem created strong demand and funding for steam engine development, including Watt s contributions. Step 6: Therefore Reason (R) is true and correctly describes a major driving force behind Watt s work on steam engines, thereby explaining the importance of his invention or improvement. Verification / Alternative check: History of science books and school textbooks often mention mine dewatering as one of the earliest and most important applications of steam engines. They explain how Watt s design improvements allowed more efficient use of steam and how this supported both mining and factory systems. This background aligns well with the Reason given and supports its role as an explanation for the Assertion. Why Other Options Are Wrong: Options that say Assertion (A) is false would contradict the conventional school level narrative, where James Watt and the steam engine are closely linked. Options that deny the truth of Reason (R) ignore the widely documented problem of water in mines and its role in the development of early industrial machinery. Therefore only the option where Reason correctly explains Assertion fits both historical facts and typical exam expectations. Common Pitfalls: Some students may know that Watt did not literally create the very first steam engine and therefore think the Assertion is technically false. However, for standard general knowledge questions, the focus is on his major contribution, and textbooks often simplify by calling him the inventor. It is important to answer according to that level of simplification in competitive exams. Final Answer: Reason (R) correctly explains Assertion (A), so the correct option is Reason (R) correctly explains Assertion (A).

Question 13

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): When common salt is kept open for a long time, it tends to absorb moisture from the air. Reason (R): Commercial common salt contains magne…

Accepted Answer

Introduction / Context: This Assertion and Reason question is from everyday chemistry. It focuses on why common salt sometimes becomes moist or lumpy when left exposed to air. The question highlights the role of deliquescent impurities, particularly magnesium chloride, in this behaviour. Understanding this explanation is useful for practical life and examinations testing basic properties of salts and hygroscopic substances. Given Data / Assumptions: Assertion (A): Common salt absorbs moisture from the air when kept open. Reason (R): Common salt contains magnesium chloride. Pure sodium chloride by itself is not strongly deliquescent at normal conditions. Commercial table salt often contains small amounts of magnesium chloride and calcium chloride as impurities. Concept / Approach: Deliquescent substances have a strong tendency to absorb water vapour from the air and can even dissolve in the absorbed water to form a solution. Magnesium chloride and calcium chloride are examples of such substances. If common salt contains these impurities, they will attract water vapour, and the entire salt mixture may appear moist or sticky. To answer the question, we must verify both the observed property and the reason involving impurities. Step-by-Step Solution: Step 1: In daily life, table salt sometimes becomes damp or forms lumps if it is left uncovered in a humid atmosphere. This supports Assertion (A) and shows that the behaviour described is real. Step 2: Pure sodium chloride in its ideal form does not strongly absorb moisture to the point of deliquescence under ordinary conditions. Step 3: However, commercial common salt is rarely completely pure. It often contains small quantities of magnesium chloride and calcium chloride as natural impurities. Step 4: Magnesium chloride and calcium chloride are deliquescent substances, which means they readily absorb moisture from the air and can dissolve in the absorbed water. Step 5: When common salt containing these impurities is exposed to moist air, the impurities absorb water vapour, become wet, and spread moisture through the salt crystals, making the entire mixture appear damp. Step 6: Therefore Assertion (A) is true, Reason (R) is also true, and the presence of magnesium chloride impurity directly explains the observed moistening of common salt. Verification / Alternative check: Chemistry textbooks often explain lump formation in salt by pointing to deliquescent impurities like magnesium chloride. They distinguish pure sodium chloride from commercial salt and note that the latter can absorb moisture because of these extra components. This confirms that Reason (R) is the correct explanation of the Assertion and not a separate unrelated fact. Why Other Options Are Wrong: Options that treat either the Assertion or the Reason as false go against well documented observations and textbook explanations. Suggesting that Reason (R) does not explain Assertion (A) is also incorrect because magnesium chloride is precisely the substance that causes moisture absorption in commercial salt. Common Pitfalls: Students sometimes think that sodium chloride itself is strongly deliquescent and ignore the role of impurities. Another confusion is mixing up hygroscopic substances, which only absorb some moisture, with deliquescent substances, which may dissolve completely. In this context, it is the impurity that is deliquescent and makes the table salt moist. Final Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A), so the correct option is Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).

Question 14

Directions: Read the Assertion (A) and Reason (R) carefully and choose the correct alternative. Assertion (A): Tamil Nadu receives most of its annual rainfall during the winter months. Reason (R): Tamil Nadu gets significant rainfall from the retrea…

Accepted Answer

Introduction / Context: This Assertion and Reason question relates to the climate of Tamil Nadu and the Indian monsoon system. Most parts of India receive the bulk of their rainfall from the southwest monsoon in the summer months. However, Tamil Nadu is a well known exception, receiving a large share of its rainfall during the later part of the year. Understanding this helps strengthen concepts in Indian climatology and regional rainfall patterns. Given Data / Assumptions: Assertion (A): Tamil Nadu gets most of its rainfall in winter. Reason (R): Tamil Nadu gets rainfall from retreating monsoons. Retreating monsoon refers to the period when the southwest monsoon withdraws and winds change direction, bringing the northeast monsoon. We focus on the months roughly from October to December as winter rainfall season for Tamil Nadu. Concept / Approach: During June to September, the southwest monsoon brings heavy rain to most parts of India, but it gives relatively less rain to the eastern coast of Tamil Nadu because this region is in the rain shadow of the Western Ghats for that wind direction. Later in the year, when the monsoon retreats and winds reverse to blow from the northeast, these winds pick up moisture from the Bay of Bengal and give rain to the Tamil Nadu coast. This northeast or retreating monsoon season becomes the main rainy period for the state. Step-by-Step Solution: Step 1: Examine Assertion (A). Climate data for Tamil Nadu show that a large proportion of annual rainfall occurs during the months of October, November, and early December. Step 2: Compared to many other Indian states, which receive maximum rainfall in the southwest monsoon, Tamil Nadu receives a major share during these later, cooler months. So Assertion (A) is true. Step 3: Reason (R) mentions rainfall from retreating monsoons, also known as the northeast monsoon. After the withdrawal of the southwest monsoon, winds reverse direction and blow from land to sea, from the northeast towards the Bay of Bengal. Step 4: As these northeast monsoon winds pass over the Bay of Bengal, they pick up moisture and then strike the eastern coast of India, especially Tamil Nadu and nearby regions. Step 5: This leads to heavy and sometimes cyclonic rainfall over Tamil Nadu during the retreating monsoon period. Therefore Reason (R) is true. Step 6: The rainfall from the retreating monsoon is precisely the cause of Tamil Nadu receiving most of its rainfall in the winter months, so Reason (R) correctly explains Assertion (A). Verification / Alternative check: Geography textbooks explicitly highlight Tamil Nadu as a state that receives heavy rainfall during the retreating monsoon and treat it as a textbook example of winter rainfall in India. They also show rainfall distribution graphs that peak in October and November for cities like Chennai. These confirm that both the Assertion and the Reason are accurate and properly linked. Why Other Options Are Wrong: Options suggesting that Assertion (A) is false ignore well known rainfall statistics for Tamil Nadu. Options claiming the Reason is false misrepresent the northeast monsoon, which is central to rainfall in the region. Saying both are true but R does not explain A is incorrect because the retreating monsoon is exactly why winter rainfall dominates in Tamil Nadu. Common Pitfalls: Some students generalise the southwest monsoon pattern for all of India and do not remember regional exceptions like Tamil Nadu and parts of Andhra Pradesh. Others may confuse winter rainfall in Tamil Nadu with western disturbances that affect northwestern India in winter. It is important to keep these mechanisms distinct. Final Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A), so the correct option is Both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).

Question 15

Directions: For the Assertion (A) and Reason (R) given below, choose the correct alternative. Assertion (A): Razia Sultan was the daughter of Iltutmish. Reason (R): Iltutmish was a rebel.

Accepted Answer

Introduction / Context: This assertion and reason type question tests knowledge of early Delhi Sultanate history and the ability to separate correct factual statements from incorrect ones. It focuses on Razia Sultan, the first and only woman to sit on the throne of the Delhi Sultanate, and her relationship to Iltutmish, one of the important rulers of the Slave Dynasty. Given Data / Assumptions: Assertion (A): Razia Sultan was the daughter of Iltutmish. Reason (R): Iltutmish was a rebel. The question asks which option correctly states the truth values of A and R and whether R explains A. We assume standard school level Indian history as reference for facts about Razia Sultan and Iltutmish. Concept / Approach: For assertion and reason questions, we must first decide independently whether the assertion is true or false and whether the reason is true or false. Only after that do we check if the reason correctly explains the assertion. The four main patterns are: both true with explanation, both true without explanation link, assertion true and reason false, or assertion false and reason true. Here, the focus is on dynastic relationships and the characterisation of a ruler as a rebel or as a legitimate monarch. Step-by-Step Solution: Step 1: Evaluate Assertion (A). Historical records state that Razia Sultan, also known as Razia al-Din, was indeed the daughter of Sultan Iltutmish, the third ruler of the Slave Dynasty of Delhi. Iltutmish considered her capable and reportedly nominated her as his successor.Step 2: Therefore, Assertion (A), which says Razia Sultan was the daughter of Iltutmish, is true.Step 3: Evaluate Reason (R). The statement says that Iltutmish was a rebel. In mainstream historical accounts, Iltutmish is not primarily known or described as a rebel. He was a former slave who rose to power and became the recognised Sultan of Delhi. He consolidated the empire and gained formal recognition from the Caliph.Step 4: Calling him simply “a rebel” is misleading and does not match standard descriptions of his role; he was a legitimate ruler, not merely a rebel chief. Thus Reason (R) is considered false.Step 5: Since A is true and R is false, the combination that correctly reflects their truth values is “A is true but R is false.” Verification / Alternative check: If Iltutmish were commonly presented in textbooks as a rebel leader, the reason might at least be arguable. However, he is consistently presented as a recognised Sultan who stabilised the Delhi Sultanate. His status as Razia father is a basic fact, whereas branding him a rebel contradicts the standard narrative. This reinforces that only the assertion is correct. Why Other Options Are Wrong: Option a would require both A and R to be true and R to explain A, which fails because R is not true. Option b also wrongly assumes that R is true. Option d suggests A is false and R is true, which contradicts the well-established fact that Razia was his daughter and the weak historical basis for describing Iltutmish as a rebel. Common Pitfalls: Students sometimes label any ruler who once opposed another authority as a “rebel” and treat that vague label as correct. Another mistake is to judge R by whether it sounds dramatic rather than whether it appears in standard exam-oriented history material. Always rely on established textbook facts when answering such questions. Final Answer: The correct choice is that Assertion (A) is true but Reason (R) is false.

Question 16

Directions: For the Assertion (A) and Reason (R) given below, choose the correct alternative. Assertion (A): The Indian Constitution came into force with effect from 26th January 1950. Reason (R): 26th January is celebrated as the Republic Day.

Accepted Answer

Introduction / Context: This question checks basic civics knowledge about the date on which the Constitution of India came into force and why 26th January is significant as Republic Day. It also tests whether the student can distinguish between a factual consequence and a true explanatory cause in an assertion–reason format. Given Data / Assumptions: Assertion (A): The Indian Constitution came into force with effect from 26th January 1950. Reason (R): 26th January is celebrated as the Republic Day. We assume standard NCERT style civics and history content about the Constitution of India and national days. The task is to judge the truth of each statement and decide whether R correctly explains A. Concept / Approach: The assertion states the key constitutional date. The reason states a national celebration associated with that date. In assertion–reason questions, even if both statements are true, R is considered the correct explanation of A only if it answers the “why” behind A. Here we must check: did the Constitution come into force on 26 January because that date is Republic Day, or is it the other way round: the date became Republic Day because the Constitution came into force then? Step-by-Step Solution: Step 1: Check Assertion (A). The Constitution of India was adopted on 26th November 1949 and came into force on 26th January 1950. Therefore, A is a correct factual statement.Step 2: Check Reason (R). 26th January is indeed celebrated every year as Republic Day in India, marking the date when India became a full republic by putting the Constitution into effect. So R is also a correct statement.Step 3: Examine the explanatory link. The Constitution did not come into force on that date because it was Republic Day. In fact, 26th January was chosen as the date for enforcing the Constitution due to its historical importance related to the 1930 declaration of Purna Swaraj (complete independence). After the Constitution came into force on that date, 26th January then became India national Republic Day.Step 4: So while both statements are true, R is not the logical reason that explains A. R describes a consequence or associated fact, not the cause behind the date chosen for enforcement. Verification / Alternative check: If R were a correct explanation, rephrasing would make sense as “The Constitution came into force on 26th January 1950 because that day is Republic Day.” This is reversed logic. Historically, the day is celebrated as Republic Day because the Constitution came into force on that date, not the other way around. This simple reversal test confirms that R is not the explanation for A. Why Other Options Are Wrong: Option a claims that R correctly explains A, which is incorrect because it mixes up cause and effect. Option c suggests that R is false, which contradicts the well-known fact of Republic Day. Option d says A is false and R is true, which is also wrong because the Constitution did come into force on 26th January 1950. Common Pitfalls: Students often mark option a whenever both statements are true, without carefully checking the direction of explanation. Another common error is to overlook prior events like the 1930 Purna Swaraj resolution, which gives deeper context to the choice of date. Always test whether R genuinely answers the “why” of A. Final Answer: Both statements are true, but Reason (R) is NOT the correct explanation of Assertion (A).

Question 17

Directions: For the Assertion (A) and Reason (R) given below, choose the correct alternative. Assertion (A): Silver is not used to make electric wires. Reason (R): Silver is a bad conductor.

Accepted Answer

Introduction / Context: This question checks basic physics knowledge about electrical conductivity and also tests logical reasoning in assertion–reason format. It focuses on why certain materials are chosen or not chosen to make everyday electric wires and challenges a common misunderstanding about silver as a conductor of electricity. Given Data / Assumptions: Assertion (A): Silver is not used to make electric wires. Reason (R): Silver is a bad conductor. We assume school level physics ideas about conductors, insulators and economic considerations. The goal is to judge the truth of A and R and to see whether R explains A. Concept / Approach: First, we must recall which materials are good electrical conductors. Then we think about why copper and aluminium are standard choices for wiring instead of silver or gold, even though those are also metals. Finally, we evaluate whether the given reason matches real scientific and practical explanations. Conductivity and cost both play important roles in such decisions. Step-by-Step Solution: Step 1: Evaluate Assertion (A). In everyday practice, household and industrial electric wires are made mainly from copper or aluminium, not from silver. So the statement that silver is not used to make electric wires, in common practical wiring, is broadly true.Step 2: Evaluate Reason (R). Silver is in fact one of the best electrical conductors among all metals. Its electrical conductivity is higher than that of copper. Therefore calling silver a bad conductor is scientifically wrong.Step 3: Compare A and R. A is essentially true because silver is not generally used for ordinary wiring. R, however, is false because its claim that silver is a bad conductor contradicts well known physical properties.Step 4: Since R is false, it cannot be a correct explanation of A. The real reasons silver is not commonly used for electric wiring are its high cost and issues of mechanical practicality, not poor conductivity. Verification / Alternative check: We can do a quick conceptual check: if silver were a bad conductor, we would never see it used in high quality electrical contacts or specialised components. In reality, silver is used in premium electrical contacts and some specialised applications precisely because of its excellent conductivity. But due to its high price, it is not economical for routine domestic wiring. This confirms that the reason given in R is misleading and incorrect. Why Other Options Are Wrong: Option a assumes both statements are true and R explains A, which fails because R is not true. Option b still assumes R is true, which is incorrect. Option d suggests that A is false and R is true, but we know that silver is rarely used for wires in normal practice while its conductivity is excellent, so that combination is also wrong. Common Pitfalls: Many learners quickly associate “not used” with “bad conductor” and accept the reason without recalling that cost, availability and strength are also important engineering factors. It is important to separate economic reasons from physical properties. Always check basic science facts such as conductivity before accepting a reason. Final Answer: The correct choice is that Assertion (A) is true but Reason (R) is false.

Question 18

Directions: For the Assertion (A) and Reason (R) given below, choose the correct alternative. Assertion (A): Vaccines prevent diseases. Reason (R): Vaccines must be given to children.

Accepted Answer

Introduction / Context: This item tests basic biology and health awareness regarding vaccination. It also checks if students can distinguish between a scientific explanation and a recommendation. Vaccines are one of the most important tools in preventive medicine, and many public health messages emphasise childhood vaccination. Given Data / Assumptions: Assertion (A): Vaccines prevent diseases. Reason (R): Vaccines must be given to children. We assume standard school biology content about immunity and vaccination. We must decide the truth of A and R and whether R explains A. Concept / Approach: In assertion–reason questions, a statement about cause or mechanism should properly explain the central idea in the assertion. Here the assertion talks about what vaccines do. The reason talks about what we should do with vaccines for children. We must ask whether “must be given to children” is a causal explanation for “prevent diseases”, or simply an important recommendation that follows from the benefit of vaccines. Step-by-Step Solution: Step 1: Evaluate Assertion (A). Vaccines work by exposing the body to a weakened or inactivated form of a pathogen or its components, which trains the immune system to recognise and fight the real infection in the future. In this way, vaccines help prevent specific infectious diseases. So A is true.Step 2: Evaluate Reason (R). Public health programmes all over the world emphasise that children should receive vaccines according to a recommended schedule. The phrase “must be given” expresses a strong recommendation for protecting child health and preventing outbreaks. As a general health guideline, R is considered true.Step 3: Check whether R explains A. The statement in R does not explain how or why vaccines prevent diseases. It does not describe immune memory, antibodies or any biological mechanism. Instead, it says what we ought to do with vaccines for children because they are beneficial. It is a recommendation, not a scientific explanation of the preventive effect.Step 4: Therefore, although both statements are correct, R is not the logical explanation of A in the sense required by assertion–reason questions. Verification / Alternative check: If R were a correct explanation of A, it should answer the question “How do vaccines prevent diseases?” or “Why do vaccines prevent diseases?”. A suitable reason would be something like “Vaccines stimulate the immune system to develop immunity against specific pathogens.” Simply saying they must be given to children describes policy or practice, not the underlying cause. This confirms that the link is not explanatory. Why Other Options Are Wrong: Option a incorrectly claims that R is the correct explanation of A. Option c and option d require one of the two statements to be false, which goes against established biological knowledge and standard health guidelines that recognise both the preventive role of vaccines and the importance of childhood immunisation. Common Pitfalls: Students often confuse “related statement” with “explanatory statement”. Because vaccines are commonly given to children, it feels natural to see R as linked to A. However, in assertion–reason questions, only a statement that describes the mechanism or cause counts as a proper explanation. It is important to read the words carefully and see whether they truly answer “why” or “how”. Final Answer: Both the assertion and the reason are true, but Reason (R) is NOT the correct explanation of Assertion (A).

Question 19

Directions: For the Assertion (A) and Reason (R) given below, choose the correct alternative. Assertion (A): Shivaji developed the guerrilla warfare. Reason (R): Shivaji feared the Mughals.

Accepted Answer

Introduction / Context: This assertion–reason question tests understanding of Maratha history and the military strategies associated with Chhatrapati Shivaji Maharaj. It contrasts Shivaji innovative use of guerrilla tactics with an incorrect psychological motive that is sometimes loosely assumed by learners. Given Data / Assumptions: Assertion (A): Shivaji developed the guerrilla warfare. Reason (R): Shivaji feared the Mughals. The question is based on typical school level Indian history about Shivaji struggle and tactics. We must decide the truth of the assertion and the reason and see if R explains A. Concept / Approach: Guerrilla warfare involves surprise attacks, speed, knowledge of terrain and hitting and running rather than fighting in large open battles. Historical records show that Shivaji made extensive and effective use of such tactics against stronger enemies. The key question is whether he did so out of fear or as a strategic choice based on the realities of geography and relative military strength. Step-by-Step Solution: Step 1: Evaluate Assertion (A). Shivaji is famous for using guerrilla warfare in the Western Ghats and adjoining regions. His armies relied on surprise raids, swift movements through hills and forests and attacking enemy camps and supply lines unexpectedly. He is often credited with systematically developing and mastering these methods in the Deccan. So A is essentially true.Step 2: Evaluate Reason (R). The reason states that Shivaji feared the Mughals. While Shivaji recognised the military strength of the Mughal Empire and other powers like the Adil Shahi rulers, historical narratives describe him as a brave and determined leader who resisted larger empires. His use of guerrilla tactics reflected strategic calculation, not simple fear.Step 3: Because the wording “feared the Mughals” suggests cowardice rather than strategic wisdom, R is not accepted as historically accurate in this school level context. It is not the correct way to explain his military innovations.Step 4: Therefore Assertion (A) is true and Reason (R) is false. A correct reason would mention factors like the hilly terrain, smaller forces and the need to avoid direct large scale battles, not fear. Verification / Alternative check: To verify, recall that many history books highlight Shivaji courage and leadership against heavy odds. He attacked strong forts, confronted large armies and often negotiated from a position of defiance, not fear. Guerrilla warfare was an intelligent response to geography and resources. This confirms that branding it as a product of fear is misleading and unsuitable as a school level explanation. Why Other Options Are Wrong: Option a assumes that R is both true and explanatory, which is not supported by historical interpretation. Option b still treats R as true, which is incorrect. Option d would require A to be false, which goes against the well known fact that Shivaji employed guerrilla tactics effectively. Common Pitfalls: A common misunderstanding is to equate avoiding direct clashes with fear, whereas in military strategy it is often a sign of tactical wisdom. Students sometimes accept emotional sounding reasons without asking whether they accurately match textbook narratives. Always compare reasons with what is actually emphasised in your study material. Final Answer: The correct evaluation is that Assertion (A) is true but Reason (R) is false.

Question 20

Directions: For the Assertion (A) and Reason (R) given below, choose the correct alternative. Assertion (A): The Himalayas once lay under the sea. Reason (R): Fossils of marine creatures are found in the Himalayan region.

Accepted Answer

Introduction / Context: This question belongs to basic physical geography and geology. It examines the idea that the Himalayan mountain range was once associated with an ancient sea and uses fossil evidence to justify this conclusion. It is a classic example of how scientists use observable clues to reconstruct Earth geological past. Given Data / Assumptions: Assertion (A): The Himalayas once lay under the sea. Reason (R): Fossils of marine creatures are found in the Himalayan region. We assume standard school geography content about plate tectonics and fossils. The question asks if A and R are true and whether R correctly explains A. Concept / Approach: Fossils provide crucial evidence for past environments. When marine fossils are found high up in mountain rocks, it suggests that those rocks were once laid down under the sea and later uplifted. In the case of the Himalayas, plate tectonics explains how the collision between the Indian plate and the Eurasian plate uplifted sediments from the ancient Tethys Sea to form the mountains. Step-by-Step Solution: Step 1: Evaluate Assertion (A). The Himalayas are known to have been formed from sediments deposited in the Tethys Sea. Over millions of years, these sediments were compressed and uplifted as the Indian plate collided with the Eurasian plate. Thus it is correct to say that the region that is now the Himalayas once lay under the sea.Step 2: Evaluate Reason (R). Geologists have discovered fossils of marine organisms such as shells and other sea life embedded in Himalayan rocks. This is well documented in geography textbooks as a key piece of evidence of the sea origin of these rocks. Therefore R is also true.Step 3: Check whether R explains A. The presence of marine fossils in rocks that are now at high altitudes strongly indicates that those rocks formed in a marine environment and later rose. This directly supports and explains the idea stated in the assertion that the Himalayas once lay under the sea.Step 4: Therefore both A and R are true and R is a correct scientific explanation for A in this school level context. Verification / Alternative check: If the Himalayas had never been under the sea, one would not expect to find fossils of marine organisms in rocks there. The match between the type of fossils and the concept of a former sea strongly supports the standard geological explanation. This is exactly how real geologists reason from evidence to conclusion, confirming that the relationship between A and R is explanatory. Why Other Options Are Wrong: Option b is incorrect because R clearly does explain A. Options c and d treat one of the statements as false, contradicting well established textbook facts about the Himalayan origin and the presence of marine fossils. There is no support for treating either A or R as false. Common Pitfalls: Some students may think the Himalayas have always been mountains and find it hard to imagine them under a sea. Others may know about fossils in general but not connect them with past environments. Remember that fossils are like clues that tell us where and how rocks were formed long ago, especially when found in unexpected places like mountaintops. Final Answer: The correct choice is that both Assertion (A) and Reason (R) are true and R is the correct explanation of A.

Assertion and Reason Questions