What is secreted by the parietal cells of gastric glands?Multiple ChoicePepsinogenPepsinHydrochloric acidMucus

The secreted substance by the parietal cells of gastric glands is hydrochloric acid.

Explanation:

Parietal cells, located in the lining of the stomach, are responsible for producing and secreting hydrochloric acid (HCl). This acid is crucial for creating a highly acidic environment in the stomach, which helps in the digestion of food and the activation of the enzyme pepsinogen into pepsin, although pepsinogen itself is secreted by chief cells, not parietal cells.

Thus, in the context of the provided multiple choice options, the correct answer is:

Hydrochloric acid.