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: Anaesthesia
Laughing gas is: March 2005 
Select and explain. 
A. Ketamine, B. Nitric oxide, C. Nitrous oxide, D. Methane
C: Nitrous oxide
Answer: C: Nitrous oxide 
Explanation: Ans. C: Nitrous oxide Nitrous oxide is known as "laughing gas" due to the euphoric effects of inhaling it, a propey that has led to its recreational use as a dissociative hallucinogen