Lichens indicate `S_O_(2)` pollution because they

Options

A. show association between algae and fungi
B. grow faster than other
C. are sensitive to `S_O_(2)`
D. flourish in `S_O_(2)` rich environment

Explanation

**Step-by-Step Solution:**

1. **Understanding Lichens**: Lichens are a symbiotic association between two organisms: algae and fungi. This means that both organisms benefit from each other in this relationship.

2. **Role of Lichens as Pollution Indicators**: Lichens are known to be sensitive to air pollution, particularly sulfur dioxide (SO2). They serve as good indicators of environmental health.

3. **Sensitivity to SO2**: Lichens do not thrive in areas with high levels of SO2 pollution. Their absence in a particular area can indicate that the air quality is poor and that SO2 is present.

4. **Evaluating the Options**:
- **Option A**: "Show association between algae and the fungi" - This is true but does not explain why they indicate SO2 pollution.
- **Option B**: "Grow faster than the other" - This is incorrect as lichens generally grow slowly.
- **Option C**: "Are sensitive to SO2" - This is correct because lichens do not grow in SO2 polluted areas.
- **Option D**: "Flourish in SO2 rich environment" - This is incorrect as lichens cannot thrive in such environments.

5. **Conclusion**: The correct answer is **Option C**: Lichens indicate SO2 pollution because they are sensitive to it and do not grow in SO2 polluted areas.

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