Ethanal (2 mol) is treated with dilute $NaOH$ and warmed. The organic product is then hydrogenated over $Ni$ (excess $H X_{2}$ ). The final product is

Answer: D

Aldol addition gives 3-hydroxybutanal, which dehydrates by E1cB (via the enolate) to but-2-enal. Excess

H X_{2}

/Ni reduces both

C = C

and

C = O

, giving

CH X_{3} CH X_{2} CH X_{2} CH X_{2} OH

, butan-1-ol.