The rate of SN2 reaction decreases with increase in steric crowding. In the given set of molecules the second molecule(Tertiary alkyl halide) is sterically crowded, hence, it is correct option. More stable carbocation formed, higher will be the reactivity of SN1. Benzyl carbocation is more reactive than aliphatic carbocation.
The deactivating groups decreases the rate of electrophilic substitution reaction. NO2 is strong deactivating group for electrophilic substitution.
In the aromatic nucleophilic substitution reactions, the intermediate formed is carbanion and, it is stabilised by NO2 at ortho or para positions.
Hence A,B,C,D all are correct.



