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': 'Number of air changes in one hour in a drawing room should be not less than \nSelect and explain. \nA. 3, B. 2, C. 4, D. 5', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]