Assertion (A) Photochemical smog is oxidising in nature.
Reason (R) Photochemical smog contains $\mathrm{NO}_2$ and $\mathrm{O}_3$, which are formed during the sequence of reactions.
Assertion (A) Carbon dioxide is one of the important green house gases.
Reason (R) It is largely produced by respiratory function of animals and plants.
Assertion (A) Ozone is destroyed by solar radiation in upper stratosphere.
Reason (R) Thinning of the ozone layer allows excessive UV radiations to reach the surface of earth.
Assertion (A) Excessive use of chlorinated synthetic pesticides causes soil and water pollution.
Reason (R) Such pesticides are non-biodegradable.
Assertion (A) If BOD level of water in a reservoir is less than 5 ppm it is highly polluted.
Reason (R) High biological oxygen demand means low activity of bacteria in water.