The process of diffusion is involved in

Options

A. respiration
B. photosynthesis
C. transpiration
D. all of these.

Explanation

To solve the question about the involvement of diffusion in various biological processes, we can break it down step by step:

### Step-by-Step Solution:

1. **Understanding Diffusion**:
- Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. This process is fundamental in many biological functions.

2. **Analyzing Respiration**:
- In respiration, plants take in carbon dioxide (CO2) from the atmosphere and release oxygen (O2). This gas exchange occurs through diffusion, as CO2 is usually more concentrated outside the plant, and O2 is more concentrated inside. Therefore, diffusion plays a key role in respiration.

3. **Analyzing Photosynthesis**:
- During photosynthesis, plants convert light energy into chemical energy, producing glucose and oxygen. The movement of these substances, especially oxygen, occurs via diffusion. Oxygen produced in the leaves diffuses out into the atmosphere, while carbon dioxide from the atmosphere diffuses into the leaves for photosynthesis.

4. **Analyzing Transpiration**:
- Transpiration is the process where water vapor is lost from the plant, primarily through small openings called stomata. Water moves from areas of higher concentration (inside the plant) to areas of lower concentration (the atmosphere) through diffusion. This process helps in nutrient uptake and cooling the plant.

5. **Conclusion**:
- Since diffusion is involved in respiration, photosynthesis, and transpiration, the correct answer to the question is **D. All of them**.

### Final Answer:
**D. All of them**

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