Which of the following compounds is most reactive in $\mathrm{S}_{\mathrm{N}} 1$ reaction?

The reactivity order of the following molecules towards $$\mathrm{S}_{\mathrm{N}} 1$$ reaction is

$$\begin{array}{ccc} \text { Allyl chloride } & \text { Chlorobenzene } & \text { Ethyl chloride } \\ \text { (I) } & \text { (II) } & \text { (III) } \end{array}$$

The major product of the following reaction is :