Spraying of oil on stagnant water controls malaria because the

Options

A. oil kills malarial parasites in mosquitoes
B. water becomes too dirty for mosquitoes
C. mosquito larvae cannot breathe
D. none of these.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Problem**: The question asks why spraying oil on stagnant water helps control malaria. We need to identify the relationship between stagnant water, mosquitoes, and malaria.

2. **Identifying the Role of Mosquitoes**: Mosquitoes are known vectors for malaria, meaning they carry the disease-causing organism, which is the protozoan Plasmodium. They breed in stagnant water, making it a breeding ground for them.

3. **Effect of Oil on Stagnant Water**: When oil is sprayed on stagnant water, it creates a thin film on the surface. This film affects the water's surface tension.

4. **Impact on Mosquito Larvae**: The larvae of mosquitoes, which are present in stagnant water, need to breathe air. The oil film prevents them from accessing the air at the water's surface.

5. **Conclusion**: Since the mosquito larvae cannot breathe due to the oil film, they cannot survive. This leads to a reduction in the mosquito population, which in turn helps control the spread of malaria.

6. **Final Answer**: The correct option is C: "Mosquito larvae cannot breathe."

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