What are lichens particularly useful for? 

A)  for indicating toxic waste sites 
B)  for indicating water pollution 
C)  for indicating pesticides 
D)  for indicating air pollution

Lichens

Symbiotic organisms composed of a fungus and a photosynthetic partner, typically algae or cyanobacteria, that live together in a mutualistic relationship.

Air Pollution

The presence of substances in the air at levels that are harmful to human health or the environment, originating from various sources like industrial activities, vehicle emissions, and natural events.

Toxic Waste

Hazardous waste causing harm to the environment or health, often produced by industrial processes.