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: Forensic Medicine
Laughing gas is ? 
Select and explain. 
A. N2O, B. Lewisite, C. H2S, D. CO2
A: N2O
Answer: A: N2O 
Explanation: Ans. is 'a' i.e., N2O