Opening of spiraclees is regulated by the

Options

A. Ostia
B. Bristles
C. Sphincters
D. Valves

Explanation

**Step-by-Step Solution:**

1. **Understanding Spiracles**: Spiracles are small openings found in the exoskeleton of insects, primarily involved in the respiratory system. They allow air to enter and exit the tracheal system, which is essential for gas exchange.

2. **Identifying the Function of Spiracles**: The primary function of spiracles is to facilitate the exchange of gases (oxygen and carbon dioxide) between the insect and the environment. They play a crucial role in respiration.

3. **Recognizing the Role of Sphincters**: Each spiracle is equipped with a muscular structure known as a sphincter. The sphincter controls the opening and closing of the spiracle, thereby regulating airflow into the tracheal system.

4. **Evaluating the Options**:
- **Ostea**: This term refers to openings in the heart of insects and is unrelated to the respiratory function of spiracles.
- **Bristles**: These are hair-like structures on the body of insects and do not play a role in respiration.
- **Sphincters**: As mentioned, sphincters are responsible for controlling the opening of spiracles, making this the correct answer.
- **Valves**: Valves are associated with the heart and are not involved in the regulation of spiracles.

5. **Conclusion**: Based on the evaluation of the options, it is clear that the opening of spiracles is regulated by sphincters.

**Final Answer**: The opening of spiracles is regulated by sphincters.

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