A) grasses
B) mosses
C) lichens
D) fossils
Correct Answer: C
Solution :
Lichens are good indicators of air pollution as these are very sensitive to \[S{{O}_{2}}\]. Pollution of \[S{{O}_{2}}\] causes intense irritation to eyes and respiratory tract. It is absorbed in the moist passage of upper respiratory tract, leading to swelling and stimulated mucus secretion. \[S{{O}_{2}}\] causes damage to higher plants, forming necrotic areas on leaf. Plants are more sensitive to \[S{{O}_{2}}\] pollution. Higher concentration of \[S{{O}_{2}}\] in air reduces the pH of leaf tissues of some trees, increasing the total sulphur content of leaves and tree bark. It affects stomatal pores, stomatal frequency and trichomes as well as chloroplast structure.
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