Benzyl amine may be alkylated as shown in the following equation $C_6H_5CH_2+R-X \to C_6H_5NHR$ Which of following alkyl aides is best suited for this reaction through $SN1$ mechanism ? -

Question

$\begin{array}{1 1} CH_3Br \\ C_6H_5Br \\ C_6H_5CH_2Br \\ C_2H_5Br \end{array}$