The most important function of hydrochloric acid in the stomach is:: (A) Destruction of bacteria, (B) Neutralization of chyme, (C) Activation of pepsinogen, (D) Stimulation of pancreatic secretion
Answer is C. Functions of HCl are: 

activation of pepsinogen to pepsin by providing acidic medium,
bacteriolytic action and
acidification of chyme which cause release of secretin and cholecystokinin hormones.