Aldehydes are generally more reactive than ketones in nucleophilic addition reactions due to steric and electronic reasons. Sterically, the presence of two relatively large substituents in ketones hinders the approach of nucleophile to carbonyl carbon than in aldehydes having only one such substituent. ELectronically, aldehydes are more recative than ketones because two alkyl groups reduce the electrophilicity of teh carbonyl more efficiently than in former.

The correct answer is option 3.

When an alkyl-substituted benzene (like toluene or any other alkyl benzene) is treated with potassium permanganate \((KMnO_4)\) in the presence of a base (such as \(KOH\)) under heating conditions, the side chain undergoes oxidation to give a carboxylic acid group (-COOH), resulting in benzoic acid. The reaction typically requires subsequent acidification (using \(H_3O^+\)) to protonate the carboxylate anion formed during the oxidation process, yielding benzoic acid.

For example if we consider the reaction in the question, then the reaction can be summarized as:

This reaction is particularly useful because it occurs irrespective of the length of the alkyl side chain, as long as there is at least one benzylic hydrogen (a hydrogen atom attached to the carbon directly bonded to the benzene ring).