The $\beta$ -Hydroxy Carbonyl Product of an Aldol Reaction Is Oftentimes Not

The $\beta$ -hydroxy carbonyl product of an Aldol reaction is oftentimes not the final isolated product, what is the explanation for this result?

A) It undergoes elimination, since water is a good leaving group.
B) The hydroxy group is oxidized to a carbonyl.
C) The hydroxy group reacts with the carbonyl to form a ketal.
D) Hydroxide is eliminated via an enolate intermediate.