Assertion (A): Aniline does not undergo Friedel-Crafts reaction.

Reason (R): $-{\mathrm{NH}}_2$ group of aniline reacts with ${\mathrm{AlCl}}_3$

Reaction between aniline and ${\mathrm{AlCl}}_3$,

$\mathrm{Ph}-{\mathrm{NH}}_2\stackrel{{\mathrm{AlCl}}_3}{\to }\mathrm{Ph}-{\mathrm{NH}}_2{{}^{+}\mathrm{AlCl}_3}^{-}$

So, during the reaction $-{\mathrm{NH}}_2$ group of aniline reacts with ${\mathrm{AlCl}}_3$ to give salt.

This is the reason why aniline does not undergo Friedel-Crafts reaction.

Hence, option (A) is correct.