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': 'Normal acid level in stomach is \nSelect and explain. \nA. 300-400 m Eq, B. 100-200 m Eq, C. 20-40 m Eq, D. 15-20 m  Eq', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]