A compound `(A)` with molecular formula `C_(5) H_(10)` gives one monochlorination product. Compound `(A)` is:

Explanation

a. `C_(5)H_(10)` has `1^(@)` of unsaturation. It should have either one double bond of should be a cyclic compound. If it has one doble, then it should give many monochlorinated products. So, it is a cyclic compound. Thus, it should be cylopentane.
will give only one monochloro product, while other cyclic isomers will give serveral products.
So,
b. The different isomers can be
i. ii. iii.
iv. v.
i.
ii.
iii.
iv.
v.
Therefore, total number of isomers `=1+4+3+4+2 =14` (excluding stereoisomers).