The most reactive of the following is (J&K CET)

Relative reactivity of aldehydes and ketones depend upon (i) inductive effect (ii) steric effect. Large number of alkyl groups on carbonyl carbon atom decreases their reactivity due to both +I-effect (these groups decreases polarity of carbonyl group) and steric effect. As ketones possess large number of alkyl groups, therefore they are less reactive than aldehydes. Aromatic aldehydes are less reactive than corresponding aliphatic aldehydes and ketones because of the resonance effect (+R-effect) of the benzene ring which increases electron density on carbonyl carbon, thereby, repelling nucleop