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 them when poured on water.

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).