Answer:
Gastrin.
Step-by-step explanation:
Digestion is the process of the breakdown of large food particle into the simpler substances with the help of digestive juice and enzymes. The digested product must be absorbed in the body.
Gastrin is the hormone that are released by the stomach lining and stimulate the secretion of hydrochloric acid. This hormone is only released after the digestion of protein and its secretion increases when the food is present in the stomach.
Thus, the correct answer is gastrin.