Site of gaseous exchange in lungs is :

Options

A. pulmonary chamber
B. trachea
C. bronchioles
D. alveoli

Explanation

**Step-by-Step Solution:**

1. **Understanding the Function of Lungs:**
- The primary role of the lungs is to facilitate the exchange of gases, which includes the intake of oxygen and the expulsion of carbon dioxide.

2. **Identifying the Components of the Respiratory System:**
- The respiratory system consists of various structures including the trachea, bronchi, bronchioles, and alveoli.
- The trachea and bronchi are primarily conducting airways that transport air to the lungs but do not participate in gas exchange.

3. **Recognizing the Site of Gas Exchange:**
- The actual site of gaseous exchange in the lungs is the alveoli.
- Alveoli are tiny, irregularly shaped air sacs that are present in large numbers within the lungs.

4. **Characteristics of Alveoli:**
- Alveoli have very thin walls, which facilitate efficient diffusion of gases.
- They are highly vascularized, meaning they have a rich blood supply, allowing for effective transport of oxygen into the blood and carbon dioxide out of the blood.

5. **Conclusion:**
- Based on the above points, the correct answer to the question regarding the site of gaseous exchange in the lungs is **alveoli**.

**Final Answer:**
The site of gaseous exchange in the lungs is the **alveoli**.

---