In $\;S_{N}2\;$ reactions , the correct order of reactivity for the following compounds : $\;CH_{3}Cl\;,CH_{3}CH_{2}Cl\;,(CH_{3})_{2}CHCl\;$ and $\;(CH_{3})_{3}CCl\;$ is :

Question

(a) $\;CH_{3}Cl > (CH_{3})_{2}CHCl > CH_{3}CH_{2}Cl > (CH_{3})_{3}CCl\;$ (b) $\;CH_{3}Cl > (CH_{3})_{2}CHCl > CH_{3}CH_{2}Cl > (CH_{3})_{3}CCl\;$(c) $\;CH_{3}CH_{2}Cl > CH_{3}Cl > (CH_{3})_{2}CH_{2}Cl > (CH_{3})_{3}CCl\;$(d) $\; (CH_{3})_{2}CH_{2}Cl > CH_{3}CH_{2}Cl > CH_{3}Cl > (CH_{3})_{3}CCl\;$