Which among the following kills harmful bacteria and other microorganisms in food, and creates an acidic environment in the stomach?

The inner lining of the stomach produces hydrochloric acid. 

The stomach lining's parietal cells secrete hydrochloric acid into the lumen or hollow space of the stomach. 

Hydrochloric acid kills harmful bacteria and other microorganisms in food, creates an acidic environment in the stomach that is hostile to bacteria and other microorganisms, activates digestive enzymes, dissolves and breaks down certain types of food, such as proteins, and helps to protect the stomach lining. 

However, excessive hydrochloric acid production can result in conditions such as gastritis and ulcers.