Lichens are best ecological indicator of

Options

A. Air pollution
B. Water pollution
C. Noise pollution
D. All of these

Answer

### Step-by-Step Solution:

1. **Understanding Lichens**: Lichens are a symbiotic association between fungi and algae. This means they consist of two different organisms that live together and benefit from each other.

2. **Components of Lichens**: In this association, the fungal component is called the mycobiont (the fungus), and the algal component is called the photobiont (the algae). The algae are autotrophic, meaning they can produce their own food through photosynthesis, while the fungi are heterotrophic, meaning they obtain their nutrients from other sources.

3. **Mutual Benefits**: The algae provide food for the fungi through photosynthesis, while the fungi offer shelter and absorb mineral nutrients and water from the environment for the algae.

4. **Sensitivity to Pollution**: Lichens are sensitive to air quality, particularly to sulfur dioxide (SO2), which is a common air pollutant. They cannot thrive in areas with high levels of pollution, especially where sulfur dioxide is present.

5. **Conclusion**: Because lichens are sensitive to sulfur dioxide and do not grow in polluted areas, they serve as excellent ecological indicators of air pollution. Therefore, the correct answer to the question is that lichens are the best ecological indicators of air pollution.