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
Number of air changes in a drawing room per hour should be at least 
Select and explain. 
A. 5-Apr, B. 4-Mar, C. 3-Feb, D. 6-May
C: 3-Feb
Answer: C: 3-Feb 
Explanation: None