Which one of the following undergoes nucleophilic substitution exclusively by SN1 mechanism?

Aliphatic SN1 reaction is carried out in two steps. In the first step, a carbocation is formed, and its formation is based on the stability of the carbocation. C6H5+CH2 > CH3+CHCH3 > CH3+CH2
In the second step, the nucleophile is attracted to the carbocation to give the final products. Hence, the order of SN1 reaction is C6H5+CH2 > CH3CH−CH3 > CH3CH2. The aryl halides e.g., chlorobenzene are less reactive compared to alkyl halides towards nucleophilic reagents in either SN2 or SN1 reaction because the carbon-halogen bond in the aryl halide is strong (due to its double bond character). So, the correct option is Benzyl chloride.