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
[{'content': 'Laughing gas is ? \nSelect and explain. \nA. N2O, B. Lewisite, C. H2S, D. CO2', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., N2O", 'role': 'assistant'}]