Which one of the following disease is caused by protozoans?

Options

A. Malaria
B. Influenza
C. AIDS
D. Cholera

Explanation

To answer the question "Which one of the following diseases is caused by protozoans?", we will analyze the options provided and identify the causative agents of each disease.

### Step-by-Step Solution:

1. **Identify the Diseases**: First, we need to list the diseases mentioned in the options. For example, let's consider malaria, influenza, AIDS, and cholera.

2. **Determine the Causative Agents**:
- **Malaria**: This disease is caused by the protozoan *Plasmodium*. It is transmitted to humans through the bite of infected female Anopheles mosquitoes.
- **Influenza**: This is a viral disease caused by the influenza virus. It is commonly known as the flu.
- **AIDS**: Acquired Immunodeficiency Syndrome (AIDS) is caused by the Human Immunodeficiency Virus (HIV), which is also a virus.
- **Cholera**: This disease is caused by the bacterium *Vibrio cholerae*, making it a bacterial disease.

3. **Analyze the Options**: Now that we have identified the causative agents:
- Malaria: Protozoan (*Plasmodium*)
- Influenza: Virus
- AIDS: Virus (HIV)
- Cholera: Bacteria (*Vibrio cholerae*)

4. **Conclusion**: Among the diseases listed, malaria is the only one caused by a protozoan. Therefore, the correct answer is malaria.

### Final Answer:
The disease caused by protozoans is **Malaria**.

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