Primary site of pulmonary gas exchange is

Options

A. Trachea
B. Alveoli
C. Larynx
D. Bronchi

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the primary site of pulmonary gas exchange. This means we need to identify where in the respiratory system the exchange of oxygen and carbon dioxide primarily occurs.

2. **Analyzing the Options**:
- **Option A: Trachea**: The trachea is the windpipe that connects the larynx to the bronchi. Its main function is to transport air to the lungs, but it is not involved in gas exchange.
- **Option B: Alveoli**: Alveoli are tiny air sacs located at the end of the bronchioles in the lungs. They are the primary site for gas exchange due to their large surface area and thin walls, which facilitate the diffusion of gases.
- **Option C: Larynx**: The larynx, or voice box, is responsible for producing vocal sounds and preventing food from entering the lower respiratory tract. It does not play a role in gas exchange.
- **Option D: Bronchi**: The bronchi are the main passageways that direct air into the lungs. While they are important for air transport, they do not participate in gas exchange.

3. **Identifying the Correct Answer**: After analyzing all the options, it is clear that the alveoli are the primary site of pulmonary gas exchange. They are specifically designed for this function due to their structure.

4. **Conclusion**: Therefore, the correct answer to the question is **Option B: Alveoli**.

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