A location with luxuriant growth of lichens on the trees indicates that the Trees are very healthy. Location is highly polluted. Location is not polluted. Trees are heavily infested.

Lichens are composed of algae and fungi living together in a symbiotic relationship. Sulfur dioxide, is a pollutant which when mixed with rainwater or air can damage lichens and does not allow them to grow due to which they act as natural indicators of air pollution. Therefore the absence of lichens indicates that the area is heavily polluted with sulfur dioxide. Thus, the correct answer is option D.