Consider the following reaction.

The major product (P) formed is :

In the first step, (NaBH_4/MeOH) selectively reduces the aldehyde group to a primary alcohol without affecting the lactam ring. Thus, the (-CHO) group is converted into (-CH_2OH), while the cyclic amide remains unchanged.

In the second step, treatment with aqueous (NaOH) under heating hydrolyzes the lactam. Hydroxide attacks the amide carbonyl carbon, leading to cleavage of the cyclic amide bond and opening of the ring to give a linear amino acid salt containing a carboxylate group and a secondary amine.

During the final acidic work-up with (H_3O^+), the carboxylate ion is protonated to form the corresponding carboxylic acid, yielding the neutral ring-opened product.

Since basic hydrolysis of a lactam under these conditions necessarily causes ring opening, the final product should be a linear amino alcohol-carboxylic acid derivative rather than a cyclic amine.

Therefore, a ring-opened structure corresponding to Option D is the expected major product. The cyclic structure shown in the provided answer key is inconsistent with the normal hydrolysis behavior of lactams under (NaOH) and heat.