Correct option (c) (II) > (I) > (III)
Explanation:
In phenyl magnesium bromide 
Ph attached with that C-atom of carbonyl group which have low electron density (higher electropositive charge).
In carbonyl compounds, aldehydes are more reactive
towards nucleophile in nucleophilic addition reaction because in ketones alkyl groups (due to + l effect) decrease the electropositive charge of carbon of carbonyl group. Hence. attraction of nucleophile decreases. Moreover in the tetrahedral intermediate aldehyde have less steric repulsion than ketolnes and also the aldehyde increases the negative charge on oxygen less in comparison of ketones.
Thus, on the basis of above reason the order of reactivity of acetone (I), acetaidehyde (II) and benzaldehyde (lII) with PhMgBr is
