Compound A (C8H9NO) on treatment with Br2/KOH gives B. B reacts with NaNO2/HCl at 273 K with evolution of N2 to give C, and C on oxidation with…

Hoffmann bromamide degradation needs a primary amide and removes one carbon: $\mathrm{C_6H_5CH_2CONH_2\to C_6H_5CH_2NH_2}$ (B). An aliphatic-type primary amine reacts with $\mathrm{HNO_2}$ to give the alcohol with $\mathrm{N_2}$ evolution: benzyl alcohol (C), which oxidises to benzoic acid. 4-Methylbenzamide would give $p$-toluidine, whose diazonium salt is stable at $273\ \mathrm{K}$ (no $\mathrm{N_2}$), and the secondary amide and anilide cannot undergo Hoffmann degradation.