Mosquitoes are vectors for
I. Dengue fever
II. Malaria
III. Cholera

Options

A. I only
B. I and II
C. II and III
D. I, II and III

Explanation

To determine which diseases mosquitoes are vectors for, let's analyze the options provided:

1. **Understanding Vectors**: Vectors are organisms that transmit pathogens from one host to another. In this case, we are looking at mosquitoes and the diseases they spread.

2. **Identifying the Diseases**:
- **Dengue Fever**: This disease is caused by the dengue virus, which is transmitted by mosquitoes, particularly the Aedes aegypti species.
- **Malaria**: Malaria is caused by the Plasmodium parasite, which is also transmitted by mosquitoes, specifically the Anopheles species.
- **Cholera**: Cholera is caused by the bacterium Vibrio cholerae. It is primarily spread through contaminated water and food, not by mosquitoes.

3. **Conclusion**: From the analysis, we can conclude that:
- Mosquitoes are vectors for **Dengue Fever** and **Malaria**.
- Mosquitoes are **not** vectors for **Cholera**.

Thus, the correct answer is that mosquitoes are vectors for:
- I. Dengue fever
- II. Malaria

**Final Answer**: I and II only.

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