Answer : 1 Air pollution Explanation : Answer: A) Air pollution Explanation: 1. Lichens are plants that grow in exposed places such as rocks or tree bark. 2. Lichens are widely used as environmental indicators or bio-indicators. They can be used as air pollution indicators, especially of the concentration of sulfur-di-oxide in the atmosphere. 3. They need to be very good at absorbing water and nutrients to grow there.
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