Why is diffusion insufficient to meet the oxygen requirements of multi- cellular organisms like humans?

Explanation

### Step-by-Step Solution:

1. **Understanding Diffusion**:
- Diffusion is the process where gases move from an area of higher concentration to an area of lower concentration. This is a natural process that occurs in many biological systems.

2. **Diffusion in Unicellular Organisms**:
- In unicellular organisms, diffusion is often sufficient for gas exchange. These organisms have a simple structure and a small size, allowing gases to diffuse quickly and efficiently to all parts of the cell.

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