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: Social & Preventive Medicine
[{'content': 'PH of drinking water \nSelect and explain. \nA. 4.5 - 6, B. 6.5 - 8.5, C. 7.5 - 9, D. 9.5', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]