JEE Main 2025 Jan 29 Shift 1, Chemistry Q16: Properties and Important Reactions of Aldehydes & Ketones

Zn-Hg / HCl is the Clemmensen reduction, which converts aldehydes and ketones to the corresponding methylene/methyl groups. It does not reduce esters or carboxylic acid derivatives under the standard conditions.

On the substrate, the ketone $\mathrm{Ar}\text{-}\mathrm{COC}{\mathrm{H}}_3$ becomes $\mathrm{Ar}\text{-}\mathrm{C}{\mathrm{H}}_2\mathrm{C}{\mathrm{H}}_3$ (ethyl), the aldehyde $\mathrm{Ar}\text{-}\mathrm{CHO}$ becomes $\mathrm{Ar}\text{-}\mathrm{C}{\mathrm{H}}_3$ (methyl), while the ester $\mathrm{Ar}\text{-}\mathrm{COO}{\mathrm{C}}_2{\mathrm{H}}_5$ is untouched.

This matches option (3).