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
[{'content': 'Gas stored in liquid form is: \nSelect and explain. \nA. Carbon dioxide, B. Nitrous oxide, C. Cyclopropane, D. Oxygen', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Nitrous oxide', 'role': 'assistant'}]