Correct Answer: Lichens

Solution : The correct option is Lichens.

Lichens are frequently used as bioindicators to measure levels of air pollution. These one-of-a-kind organisms, generated by a symbiotic relationship between fungus and photosynthetic algae, are extremely susceptible to pollutants such as sulphur dioxide, nitrogen dioxide, heavy metals, and particle matter. Researchers may assess air quality and possible pollution concerns in a region by monitoring the presence and condition of particular lichen species. This data is useful for environmental evaluations and policy choices about air quality and ecosystem health.