Observe the pictu

(a) Mask is covering the nose and mouth of the police man.

(b) He is putting a cover(mask) on his nose so that he do not inhale the dust particles and harmful gases which are produce by the moving vehicles (automobiles) as harmful gases make it difficult to breath and may cause lung diseases like asthma.

(c) The quality of the air is Bad. The harmful gases released by the vehicles spread and contaminate the air. Thus making the quality of air bad.