Q.20. Consider the following reactions,

The end product 'S' is :
(a)

(b)

(c)

(d)

in the first reaction bromine will get attached to the meta position because NO2 is a deactivating and a meta directing group
in second catalytic hydrogenation will convert NO2 to NH2 
third is diazotization reaction and in fourth Cl will replace N2+Cl-