Directions: For the Assertion (A) and Reason (R) given below, choose the correct alternative. Assertion (A): We feel colder on mountains than on plains. Reason (R): Temperature decreases with altitude.

Introduction / Context:
This question belongs to basic climatology and geography. It connects everyday experience of feeling colder in hill stations and mountain regions than in low lying plains with a fundamental atmospheric principle: temperature variation with height. It uses assertion–reason format to see if students understand that the environmental lapse rate explains the difference.

Given Data / Assumptions:

• Assertion (A): We feel colder on mountains than on plains.
• Reason (R): Temperature decreases with altitude.
• We assume standard school geography concepts about temperature lapse rate.
• The task is to evaluate truth values and the explanatory link.

Concept / Approach:
In the troposphere, which is the lowest layer of the atmosphere, temperature generally decreases with increasing height above sea level. This is known as the normal lapse rate. Mountainous areas are at higher altitudes than surrounding plains, so their air temperature is usually lower, which leads to the feeling of colder climate in hill stations and mountain tops.

Step-by-Step Solution:
Step 1: Evaluate Assertion (A). It is a common fact that people visit hill stations to escape summer heat because they are cooler than the plains. So the assertion that we feel colder on mountains than on plains is clearly true as a general statement.Step 2: Evaluate Reason (R). According to basic geography, with every increase in altitude, the temperature of the atmosphere generally decreases at a certain rate, often averaged as about 6.5 degrees Celsius per 1000 metres. This is a well known principle, so R is also true.Step 3: Check whether R explains A. Mountains are at higher altitudes compared to surrounding plains. Because temperature decreases with height, regions at higher altitude experience lower temperatures. This directly explains why we feel colder on mountains than in low lying plains.Step 4: Therefore both A and R are true and R is the correct explanation of A.

Verification / Alternative check:
Think of specific examples such as Shimla or Ooty compared with nearby plains in summer. Weather reports consistently show lower temperatures in these hill stations. The difference cannot be explained by latitude alone, because places at similar latitude but lower height are warmer. The altitude based lapse rate is the primary reason, confirming that R best explains A.

Why Other Options Are Wrong:
Option b incorrectly suggests that R is not the explanation. Options c and d require one of the statements to be false, which would contradict both everyday experience and well established atmospheric science.

Common Pitfalls:
Some students may confuse height above sea level with distance from the equator or longitude, or may think that mountains are colder only because they are further from the ground. The proper reasoning is that the structure of the atmosphere and processes of rising and cooling air masses cause temperature to fall with altitude. Remember to link the phenomenon directly to the lapse rate concept.

Final Answer:
The correct choice is that both Assertion (A) and Reason (R) are true and R is the correct explanation of A.