Cumene on treatment with $KMn{O}_4$ gives :-

The correct option is B
Oxidation of Alkyl Benzenes: When treated under strong oxidising conditions, benzylic-H systems are oxidised all the way to the carboxylic acid. The alkyl substituent can be methyl-, $1^o$ or $2^o$ alkyl.
$3^o$ alkyl are not oxidised because they lack a benzylic-H (Must have at ​
least 1 benzylic hydrogen​.)
Cumene on treatment with $KMn{O}_4$ gives benzoic acid. The side chain of benzene is oxidized to $-COOH$ group.