Lichens can be used

Options

A. Bioindicator for water and air pollution
B. Initial vegetation for waste lands
C. Source of wood
D. To check air pollution

Answer

**Step-by-Step Solution:**

1. **Understanding Lichens**: Lichens are a symbiotic relationship between a fungus and an alga. This means that both organisms benefit from each other. The fungus provides structure and protection, while the alga performs photosynthesis to produce food.

2. **Role of Lichens in the Environment**: Lichens are sensitive to environmental changes, particularly air quality. They are known to be affected by pollutants, especially sulfur dioxide (SO2), which is a common air pollutant.

3. **Lichens as Bioindicators**: Due to their sensitivity to air pollution, lichens can serve as bioindicators. This means that their presence or absence can indicate the level of pollution in an area. If lichens are absent, it suggests high levels of pollution, while their presence indicates a cleaner environment.

4. **Analyzing the Options**:
- **Option A**: Bioindicator for water and air pollution - This is correct as explained above.
- **Option B**: Initial vegetation for wasteland - While lichens can colonize barren areas, they are not specifically known for this role.
- **Option C**: Source of wood - This is incorrect as lichens do not provide wood.
- **Option D**: To check air pollution - This is partially correct but does not encompass their role in water pollution.

5. **Conclusion**: The best answer to the question "Lichens can be used" is **Option A: bioindicator for water and air pollution**.

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