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: Microbiology
Disinfection of the rooms can be done by using 
Select and explain. 
A. 20% phenol, B. High efficiency particle arrestors, C. 40% formaldehyde vapour, D. Chlorine gas
C: 40% formaldehyde vapour
Answer: C: 40% formaldehyde vapour 
Explanation: None