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
Operation theatres are sterilized by - 
Select and explain. 
A. Carbolic acid spraying, B. Washing with soap and water, C. Formaldehyde, D. ETO gas
C: Formaldehyde
Answer: C: Formaldehyde 
Explanation: None