A substance provided by the stomach, necessary for the digestion of food, is called:

Hydrochloric acid (HCl) is a substance produced by the stomach lining. It plays a crucial role in

digestion by creating an acidic environment, which helps in the breakdown of food, activates

digestive enzymes like pepsin, and kills harmful bacteria ingested with food. The other options are:

Glycogen: A stored form of glucose found in the liver and muscles, not directly involved in digestion.

Insulin: A hormone produced by the pancreas that regulates blood glucose levels, not involved in

digestion in the stomach.

Glucose: A simple sugar that is an end product of carbohydrate digestion, not a substance produced

by the stomach.

Reference:

"Digestive System: The Stomach." Johns Hopkins Medicine,

https://www.hopkinsmedicine.org/health/wellness-and-prevention/the-stomach