Why Do Aldehydes Undergo Nucleophilic Addition Reactions While Esters Undergo

Multiple Choice

Why do aldehydes undergo nucleophilic addition reactions while esters undergo nucleophilic acyl substitution reactions?

A) The carbonyl carbon of an ester is more electrophilic than that of an aldehyde.
B) Aldehydes are more sterically hindered than esters.
C) Once the nucleophile adds to an aldehyde,the tetrahedral intermediate is too sterically hindered to eliminate one of the attached groups.
D) The ester carbonyl carbon is sp3 hybridized while the aldehyde carbonyl carbon is sp2 hybridized.
E) Once the nucleophile adds to an aldehyde,neither H- nor R- can be eliminated since they are strongly basic.