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
Which is not a Vapour phase disinfectants 
Select and explain. 
A. Ethylene oxide, B. Thiomersal, C. Formaldehyde gas, D. Betapropiolactone
B: Thiomersal
Answer: B: Thiomersal 
Explanation: Vapour phase disinfectants - Ethylene oxide, Formaldehyde gas, BPL.