The correct option is A rennin
Rennin is a proteolytic (protein-digesting) enzyme synthesized by the chief cells in the stomach. Its role in digestion is to curdle or coagulate milk in the stomach, a process of considerable importance in infants. The coagulation of the milk hinders its rapid flow through the stomach and thus gives the digestive enzymes the opportunity for acting on it.
Trypsin is a proteolytic enzyme that is a part of pancreatic juice, and catalyzes digestion in the small intestine.
Erepsin is a mixture of protein-digesting enzymes found in intestinal juice.
Chymotrypsin is another proteolytic enzyme found in pancreatic juice.