Final answer:
The correct answer is C) intrinsic factor. HCl secretion is essential for digestion in the stomach, and intrinsic factor is necessary for the absorption of vitamin B12 in the small intestine.
Step-by-step explanation:
The correct answer is C) intrinsic factor.
Hydrochloric acid (HCl) secretion is essential for digestion in the stomach. Among the various cells in the gastric glands, the parietal cells produce both HCl and intrinsic factor. HCl is responsible for the high acidity of the stomach contents, which helps activate the protein-digesting enzyme, pepsin, and denature proteins for enzymatic digestion. Intrinsic factor, on the other hand, is necessary for the absorption of vitamin B12 in the small intestine.