Lichens are very sensitive to :

Options

A. `O_(2)`
B. `CO_(2)`
C. `N_(2)`
D. `SO_(2)`

Answer

**Step-by-Step Solution:**

1. **Understanding Lichens**: Lichens are symbiotic organisms formed from a partnership between fungi and algae or cyanobacteria. They are known for their sensitivity to environmental changes.

2. **Identifying Sensitivity**: The question asks what lichens are particularly sensitive to among the given options: Oxygen, Carbon Dioxide, Nitrogen, and Sulphur Dioxide.

3. **Analyzing the Options**:
- **Oxygen**: Lichens require oxygen for respiration, but they are not particularly sensitive to its levels.
- **Carbon Dioxide**: Lichens use carbon dioxide for photosynthesis, and again, they are not sensitive to its levels.
- **Nitrogen**: While nitrogen is essential for growth, lichens are not specifically sensitive to it.
- **Sulphur Dioxide**: This is a pollutant that can negatively affect lichens. They are known to be very sensitive to air pollution, particularly sulphur dioxide, which can lead to their decline.

4. **Conclusion**: Based on the analysis, the correct answer is that lichens are very sensitive to **Sulphur Dioxide**.

5. **Final Answer**: The correct option is **4. Sulphur Dioxide**.

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