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
Pepsinogen is activated by : 
Select and explain. 
A. Enterokinase, B. Low pH, C. Trypsin, D. Chymotrypsin
B: Low pH
Answer: B: Low pH 
Explanation: B i.e. Low pH