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
The best sterilization method for a hand-piece is 
Select and explain. 
A. Ethylene oxide gas, B. dry heat, C. Chemical vapour, D. all the above
A: Ethylene oxide gas
Answer: A: Ethylene oxide gas 
Explanation: None