In respiration, exchange of gases occurs on the principle of............

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the principle on which gas exchange occurs during respiration.

2. **Identifying the Process of Respiration**: Respiration involves the intake of oxygen and the expulsion of carbon dioxide. This process is crucial for cellular metabolism.

3. **Locating the Site of Gas Exchange**: The primary site for gas exchange in the human body is the alveoli, which are tiny air sacs located in the lungs.

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