Correct Answer - A::B
`{:(underset((A))underset("Propanaldehyde")(CH_(3)CH_(2)CHO)" "underset((B))underset("Benzaldehyde")(C_(6)H_(5)CHO)),(underset((C))underset("2-Methylpropanaldehyde")(CH_(3)-overset("CH"_(3))overset("| ")"CH"-CHO)" "underset((D))underset("2,2-Dimethylpropanaldehyde")(CH_(3)-overset("CH"_(3))overset("| ")underset("CH"_(3))underset("| ")"C "-CHO)):}`
As only propanaldehyde (A) and 2-methylpropan-aldehyde (C) have `alpha`-hydrogen atom and as such can undergo aldol condensation
