Benzene diazonium chloride on reaction with $\mathrm{KCN}$ in the presence of $\mathrm{CuCN}$ yields X. X on hydrolysis yields Y. Y can also be obtained from

${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{Cl}\stackrel{\mathrm{KCN}+\mathrm{CuCN}}{\to }{C}_6{\mathrm{H}}_5\mathrm{CN} \left(\mathrm{X}\right)$

${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{CN}\stackrel{{\mathrm{H}}_2\mathrm{O}}{\to }{C}_6{\mathrm{H}}_5\mathrm{COOH} \left(\mathrm{Y}\right)$

And this $Y$, benzoic acid can also be obtained by the reaction of toluene by oxidation of ${\mathrm{KMnO}}_4$.

${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{CH}}_3\stackrel{{\mathrm{KMnO}}_4}{\to }{\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COOH}$

Therefore, option B is correct.