Answer: option C) hydrochloric acid.
Justification:
The only acid produced in the stomach, and main constituent of the gastric juice, is the hydrochloric acid (HCl).
This acid is respondible for thte low pH in the gastric juice, in a range of 1.5 to 3.5 according to the literature.
That acidity is not resisted by many pathogens which, therfore, will be killed.