Question

Which is used as an air pollution indicator?

• A. Algae
• B. Fungi
• C. Bacteria
• D. Lichens

Hint:

Lichens are the canaries of ecosystems — their absence signals air pollution.

Answer 1

The Correct Option is D

Lichens are symbiotic organisms (algae + fungi).
They are highly sensitive to air pollutants, especially sulphur dioxide.
If lichens are absent in an area, it may indicate high pollution levels.
They are called bioindicators due to this sensitivity.