Preen gland occurs in

Options

A. reptilia
B. aves
C. pisces
D. mammalia

Answer

### Step-by-Step Solution:

1. **Understanding the Preen Gland**: The preen gland is a specific type of gland found in certain animals. It is important to identify which animals have this gland.

2. **Identifying the Animal Group**: The preen gland is primarily associated with birds, which belong to the class Aves.

3. **Location of the Preen Gland**: The preen gland is located dorsally at the base of the tail of birds. This positioning is crucial for its function.

4. **Function of the Preen Gland**: The preen gland secretes a substance known as preen oil. This oil is used by birds to coat their feathers, making them waterproof and preventing them from getting wet.

5. **Analyzing the Options**:
- **Reptiles**: They have dry skin and do not possess preen glands.
- **Aves (Birds)**: They have the preen gland, also known as the oil gland or uro-pygial gland.
- **Pisces (Fish)**: Fish have mucous-secreting glands but do not have preen glands.
- **Mammalia (Mammals)**: Mammals have various glands but do not have preen glands.

6. **Conclusion**: Based on the analysis, the correct answer to the question "Preen gland occurs in" is **Aves (Birds)**.