Haloalkanes And Haloarenes

Arrange the compounds \(\mathrm{A}, \mathrm{B}, \mathrm{C}\) and \(\mathrm{D}\) in the increasing order of their reactivity towards \(\mathrm{S_N}1\) reaction.

$$ \begin{aligned} & \mathrm{A}=\mathrm{C}_6 \mathrm{H}_5 \mathrm{CH}_2 \mathrm{Cl} \\ & \mathrm{B}=\mathrm{C}_6 \mathrm{H}_5 \mathrm{Cl} \\ & \mathrm{C}=\mathrm{CH}_2=\mathrm{CH}-\mathrm{Cl} \\ & \mathrm{D}=\mathrm{CH}_3-\mathrm{CH}_2-\mathrm{Cl} \end{aligned}$$