Answer : (B) $\alpha$-amino acids

Step 1 — Recall what a protein is

A protein is a polymer (polypeptide) built from many amino acid units joined by peptide bonds $-CO-NH-$.

Step 2 — Note which amino acids occur naturally

All the amino acids obtained from natural proteins have the $-NH_2$ group attached to the carbon immediately next to the $-COOH$ group. That carbon is the $\alpha$-carbon, so they are called $\alpha$-amino acids :

$$H_2N-\underset{|}{\overset{R}{C}}H-COOH$$

Step 3 — Write the hydrolysis

Complete hydrolysis breaks every peptide bond and releases the individual monomer units :

$$\text{Protein} + n\,H_2O \xrightarrow{H^+ \text{ or enzyme}} n\ (\alpha\text{-amino acids})$$

Step 4 — Reject the other options

Polypeptides are only the partial hydrolysis products, not the final ones.

Enzymes are themselves proteins, not hydrolysis products.

Glucose comes from the hydrolysis of carbohydrates, not proteins.