This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fumigants & Asphyxiants, 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., N2OSpecial gaseso Sewer gas - H2S with CO2 and methane.o Marsh gas - Methaneo War gases :Tear gas - (i) Bromobenzylcyanide (BBC), (ii) Chloroacetophenone (CAP)Blister gas - Mustard gas and BAL (Lewisite) gasSickening gas - Diphinyl-amine-chlor-arsineLaughing gas - N2O