The function of pineal body is to

Options

A. lighten the skin colour
B. control sexual behaviour
C. regulate the period puberty
D. all of these

Explanation

### Step-by-Step Solution:

1. **Identify the Pineal Body**: The pineal body, also known as the pineal gland, is a small, conical structure located in the brain. It is reddish-grey in color and highly vascularized.

2. **Function of the Pineal Body**: The primary function of the pineal body is to secrete the hormone melatonin.

3. **Role of Melatonin**:
- Melatonin is involved in regulating sleep-wake cycles (circadian rhythms).
- It plays a role in making skin color lighter in certain animals.
- In some species, melatonin influences the functioning of gonads (reproductive organs).

4. **Impact on Sexual Behavior and Puberty**:
- The pineal body, through melatonin, can regulate sexual behavior and influence the timing of puberty.
- This regulation is particularly important in certain animals where seasonal changes affect reproductive cycles.

5. **Conclusion**: Based on the functions of the pineal body, we can summarize that it is responsible for:
- Secretion of melatonin
- Regulation of skin color
- Control of sexual behavior
- Regulation of puberty

6. **Final Answer**: Therefore, the correct answer to the question "The function of pineal body is to" is option 4: "All of these."