Answer: A - Propanone and ethanal.
Step-by-step explanation:
Aldol condensation may be defiend as a reaction which involves an enol or an enolate ion with a carbonyl compound to form a beta-hydroxyaldehyde (β-hydroxyaldehyde or β-hydroxyketone), which is accompanied by dehydration to give a conjugated enone.
In this case, Propanone and ethanal will undergo condensation reaction to produce pent-3-ene-2-one.
It is important to note that propanone is an enol.
Therefore, the pair of reactants that will undergo aldol condensation to produce pent-3-ene-2-one? is Propanone and ethanal.