HCI present in the gastric juice helps in digestion by converting pepsinogen to pepsin.
The gastric juice, which contains pepsin, HCl, and mucus, is released by the gastric gland in the stomach wall. The acidic state of the food is provided by the HCl in the juice. When pepsinogen (an inactive enzyme) comes into contact with acidic food, it converts into pepsin. Pepsin is an enzyme which breaks proteins into peptides (simpler molecules).
Hence, option B is the correct answer.