Where does the gaseous exchange take place in land animals?

Options

A. Nostrils
B. Trachea
C. Skin
D. Alveoli

Answer

**Step-by-Step Solution:**

1. **Understanding Gaseous Exchange**: Gaseous exchange refers to the process where oxygen is taken into the body and carbon dioxide is expelled. This process is crucial for respiration in animals.

2. **Identifying Structures Involved**: In land animals, several structures are involved in the process of gaseous exchange, including nostrils, trachea, skin, and alveoli.

3. **Role of Nostrils**: Nostrils are the external openings that allow air to enter the respiratory system. They serve as the entry point for oxygen but are not the site of exchange.

4. **Function of Trachea**: The trachea is a tube that connects the nostrils to the lungs. It carries air to the lungs but does not facilitate the exchange of gases.

5. **Skin Respiration**: While some animals like amphibians can exchange gases through their skin, this is not the primary method for most land animals, particularly mammals.

6. **Alveoli as the Main Site**: The alveoli are tiny air sacs located within the lungs. They are the primary site for gaseous exchange in land animals. Here, oxygen from the air is absorbed into the bloodstream, and carbon dioxide is released from the blood to be exhaled.

7. **Conclusion**: Therefore, the main site of gaseous exchange in land animals is the alveoli.

**Final Answer**: The gaseous exchange in land animals takes place in the alveoli.

---