Identify `(A)` to `(G)`.

Explanation

`(A)` is alkane (since `D.U.` is zero). Write all the possible structures or `(A)` and find out the structure that gives three isomers on monochlorination.

According to the problem, (A) can be either `(I)` or `(III)` . However, these three isomers of monochloro derivatives of `(I)` will undergo dehydrohalogenation will alc. `KOH`. So, `(A)` can be (III)
(A)implies 2,2-Dimethyl pentane, (B)implies 1-Chloro-2,2-dimethyl butane, (C)implies3- Chloro-2,2-dimethyl butane, (D)implies1-Chloro-3,3-dimethyl butane, (E)implies 3,3-Dimethyl but-1-ene, (F)implies 2-Chloro-2,3-dimethyl butane, (G)implies 2,3-Dimethyl butane.