How

A$)1$

B$)2$

C$)4$

D$)3$

An unknown compound, $C_9{H}_{12},$ gave the following NMR spectrum:

Triplet at $1\mathrm{.}21ppm(3H)$ Singlet at $2\mathrm{.}30ppm(3H)$ Quartet at $2\mathrm{.}60ppm(2H)$ cinglet at $7\mathrm{.}04ppm(4H)$ What is the structure of the compound?

A$)1$

B$)$ II

C$)$ III

D$)$ IV

$7$