This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Pepsinogen is activated by : \nSelect and explain. \nA. Enterokinase, B. Low pH, C. Trypsin, D. Chymotrypsin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Low pH', 'role': 'assistant'}]