Final answer:
Rennet is the product from the stomach of suckling calves used to make cheese, as it contains an enzyme that aids in coagulating milk for cheese production.
Step-by-step explanation:
The product from the stomach of suckling calves that is used to make cheese is rennet. Rennet contains an enzyme that helps digest milk protein, which is crucial in the cheese-making process to coagulate milk, separating it into curds and whey. Although other enzymes like pepsin, lipase, and trypsin play roles in digestion, it is rennet that is traditionally harvested from the lining of the stomach of suckling calves to assist in cheese production.