This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous General Anesthesia, Subject name: Anaesthesia
Anaesthetic agent not metabolized by body is? 
Select and explain. 
A. N20, B. Gallamine, C. Sevofluorane, D. Halothane
A: N20
Answer: A: N20 
Explanation: Ans. (a) N20Ref: Miller's 7thedch: 24