Final answer:
Hydrochloric acid from the stomach is neutralized in the small intestine by option B) bicarbonate from the pancreas, ensuring the proper pH for intestinal enzymes to work.
Step-by-step explanation:
Hydrochloric acid (HCl) from the stomach is neutralized in the small intestine by B) Bicarbonate from the pancreas.
The stomach produces hydrochloric acid to create a highly acidic environment essential for the enzyme pepsin to break down proteins into smaller polypeptides. As the acidic chyme moves into the small intestine, the pancreas releases sodium bicarbonate to neutralize the acid, creating a suitable alkaline environment for the intestinal enzymes, such as trypsin and chymotrypsin, to function effectively in digesting proteins further into amino acids.