Since the compound ' \(\mathrm{C}\) ' with molecular formula \(\mathrm{C}_6 \mathrm{H}_7 \mathrm{~N}\) is formed from compound ' \(\mathrm{B}\) ' on treatment with \(\mathrm{Br}_2 \mathrm{KOH}_2\), therefore, compound ' \(\mathrm{B}\) ' must be an amide and ' \(\mathrm{C}\) ' must be an amine.
The only amine having the molecular formula \(\mathrm{C}_6 \mathrm{H}_7 \mathrm{~N}\), i.e., \(\mathrm{C}_6 \mathrm{H}_5 \mathrm{NH}_2\) is aniline.
Since ' \(\mathrm{C}\) ' is aniline, therefore, the amide from which it is formed must be benzamide \(\left(\mathrm{C}_6 \mathrm{H}_5 \mathrm{CONH}_2\right)\). Thus, compound 'B' is benzamide.
Since compound ' \(\mathrm{B}\) ' is formed from compound 'A' with aqueous ammonia and heating, therefore, compound 'A' must be benzoic acid.