The exchange of gases in the alveoli of the lungs takes place by

Options

A. passive transport
B. active transport
C. osmosis
D. simple diffusion.

Explanation

To answer the question regarding how the exchange of gases in the alveoli of the lungs takes place, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding the Structure**: The alveoli are tiny air sacs in the lungs where gas exchange occurs. They are surrounded by a network of blood capillaries.

2. **Composition of Gases**: The air in the alveoli is rich in oxygen (O2), while the blood in the capillaries contains a higher concentration of carbon dioxide (CO2).

3. **Concentration Gradient**: The process of gas exchange relies on the concentration gradient. In the alveoli, the concentration of oxygen is higher compared to the concentration of oxygen in the blood. Conversely, the concentration of carbon dioxide in the blood is higher than that in the alveoli.

4. **Process of Diffusion**: Gas exchange occurs through a process called passive diffusion. This means that gases move from an area of higher concentration to an area of lower concentration without the need for energy.

5. **Mechanism of Exchange**: Oxygen diffuses from the alveoli into the blood capillaries, while carbon dioxide diffuses from the blood into the alveoli. This exchange continues until equilibrium is reached, where the concentrations of gases are balanced.

6. **Conclusion**: Therefore, the exchange of gases in the alveoli of the lungs takes place by passive diffusion (or simple diffusion).

### Final Answer:
The exchange of gases in the alveoli of the lungs takes place by passive diffusion.

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