Answer:
HCl secretions convert pepsinogen to the active hormone pepsin. A: parietal paracrine (also known as enteroendocrine cells) in the gastric pits produce pepsinogen.
Step-by-step explanation:
Hydrochloric acid (HCL) helps in protein digestion by providing H+, with which pepsinogen is activated. Pepsinogen is produced by the main cells in 'gastric glands' of the body and 'antrum' of the stomach.
Parietal cells are 'epithelial' cells which secrete HCL. They are found in gastric glands in the lining of fundus and cardia of stomach. The main component of gastric acid is parietal cells. That's why option A is the correct answer as these cells are found in gastric glands that produce pepsinogen.