Identify the glands present in birds.

Options

A. Preen gland
B. Sebaceous gland
C. Sweat gland
D. Mammary gland

Answer

### Step-by-Step Solution:

1. **Understanding Glands in Birds**:
- Birds have specific glands that serve various functions. It is essential to identify which glands are present in birds.

2. **Identifying the Green Gland**:
- The green gland, also known as the oil secretory gland, is found in birds. This gland is located in the follicles of the feathers and is responsible for secreting oil that helps in the maintenance and care of feathers.

3. **Exclusion of Other Glands**:
- Other glands such as sebaceous glands, sweat glands, and mammary glands are not present in birds.
- **Sebaceous Glands**: Found in mammals, they secrete sebum for moisture and are associated with hair follicles.
- **Sweat Glands**: Also found in mammals, these glands help in regulating body temperature through sweat.
- **Mammary Glands**: These are milk-producing glands found only in mammals.

4. **Conclusion**:
- Based on the information, the only gland present in birds is the green gland (oil secretory gland).

### Final Answer:
The glands present in birds include the green gland (oil secretory gland).

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