B is the correct answer, but not for the reasons you have given.
4-Me-benzaldehyde cannot self-condense, and is a far more reactive electrophile than acetophenone. Acetophenone has a pKa of around 16 so will readily undergo base-catalysed aldol reaction with the aldehyde. This is the only reaction that will occur. All the other sets of reactants shown are likely to undergo self-condensation as well as cross-condensation giving a mixture of products.