Among the given compounds, the most susceptible to nucleophilic attack at the carbonyl group is

The positive charge on carbon is enhanced due to electron-with drawing nature of cholrine.

Acid chlorides are the aldehyde and acid compounds that are most vulnerable to ${\mathrm{Nu}}^{\ominus }$ assault because

(i) Strong -I effect 

(ii) Weak +R effect of Cl atom

(iii) Good leaving group Cl⁻

Because carbonyl carbon has the greatest $e^{\ominus }$ deficit, the solution is $C{H}_{3}COCl$.