Which of the following give benzoic acid on heating with hot alkaline $\mathrm{KMnO}{}_4$ followed by acidification?

Toluene, ethylbenzene and benzyl alcohol all carry a benzylic carbon bearing hydrogen, which is oxidised to the carboxyl group (the extra carbon of ethylbenzene is lost as $\mathrm{CO}{}_2$). tert-Butylbenzene has no benzylic hydrogen and is unchanged.