why why option 2 is the answer
Answers
In order to carry out Electrophilic Substitution Reaction, the substrate should be a good nucleophile. And if there is a group on the substrate which gives a +I effect, it becomes a better nucleophile and if there is a group attached which gives -I effect it will be a weaker nucleophile.
So in (1), An electron withdrawing group is placed on the substrate which will eventually give -I effect hence weakening the nucleophile.
In (2), a halide is placed on the meta position which is deactivating but ortho para directing group. It also shows some +I effect due to its electron withdrawing property. So it is a weaker nucleophile but stronger as compared to (1)
In (3), an alkyl group is placed on substrate which is an electron donating group and shows +I effect, thus strengthening the nucleophile.
In (4), A good electron donating group is present, which shows really good +I effect thus making it the best nucleophile in all four.
That's why the order of reactivity is 4>3>2>1