A flagellum is present at one end of a protozoan. It is :

Options

A. Planaria
B. Paramecium
C. Hydra
D. Leishmania

Explanation

To determine which protozoan has a flagellum at one end, we can analyze the options provided: Planaria, Paramecium, Hydra, and Leishmania.

### Step-by-Step Solution:

1. **Identify the Organisms**:
- Planaria: This is a type of flatworm, not a protozoan.
- Paramecium: This is a ciliated protozoan, which means it has cilia all over its body, not a flagellum.
- Hydra: This is a simple multicellular organism (a cnidarian) and does not have a flagellum.
- Leishmania: This is a protozoan that is known to have a flagellum at one end.

2. **Determine the Characteristics**:
- Leishmania is a flagellated protozoan, which means it has a whip-like structure (flagellum) that aids in its movement.
- It is a parasite, which means it lives on or in a host organism and derives nutrients at the host's expense.

3. **Conclusion**:
- Among the options given, Leishmania is the only organism that has a flagellum at one end, making it the correct answer.

### Final Answer:
The protozoan with a flagellum present at one end is **Leishmania**.

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