Why are lichens considered indicators of air pollution?

A. वे sulphur dioxide जैसे pollutants के प्रति sensitive होते हैं / They are sensitive to pollutants like sulphur dioxide

Step 1: Identify pollution biology concept. Step 2: Lichens are sensitive to air pollutants so they are often less common in polluted areas. Step 3: Remember absence of lichens as a pollution clue.

Step 1: pollution biology concept पहचानें। Step 2: Lichens air pollutants के प्रति sensitive होते हैं इसलिए polluted areas में कम मिलते हैं। Step 3: Lichens absent means pollution संकेत याद रखें।