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': 'In living rooms, number of air changes in one hour should be: March 2013 \nSelect and explain. \nA. 2-Jan, B. 3-Feb, C. 4-Mar, D. 5-Apr', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B i.e. 2-3 Air changes per hour is a measure of how many times the air within a defined space (normally a room or house) is replaced. It is recommended that in the living rooms, there should be 2 or 3 air changes per hour; in work rooms and assemblies 4 to 6 air changes.', 'role': 'assistant'}]