JEE Main · 2024 · 05 Apr 2024 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

Toluene is oxidised by hot alkaline $KMn{O}_4$ to potassium benzoate (A); acidification with $H_3{O}^{+}$ gives benzoic acid (B); bromination with $B{r}_2/FeB{r}_3$ (the $-COOH$ group directs meta) gives a bromobenzoic acid (C).
Counting $\pi$ bonds in C: the benzene ring contributes 3 (from its three formal C=C bonds) and the carboxylic acid carbonyl contributes 1 (C=O). Total $=3+1=4$, independent of exactly where the ring is brominated.