There Are Several Variations of the Aldol Reaction $\alpha$ -Hydrogens Are Able to Form a Single Aldol Condensation Product

There are several variations of the Aldol reaction. Which of the following types of reactants leads to only one possible product with the Aldol condensation reaction?

A) Two different aldehydes with $\alpha$ -hydrogens are able to form a single aldol condensation product.
B) Two different ketones with $\alpha$ -hydrogens are able to form a single aldol condensation product.
C) Any aldehyde and ketone mixed together can react to form a single condensation product.
D) Any pair of aldehyde or ketone reactants where one of the reactants has no $\alpha$ -hydrogens will lead to a single aldol product.