This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthetic Equipments, Subject name: Anaesthesia
[{'content': 'PIN number of nitrous oxide is: \nSelect and explain. \nA. 2, 5, B. 3, 5, C. 2, 6, D. 3, 6', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans: b (Nitrous oxide)Pin index for gasesOxygen-2,5Nitrous oxide-3,5Cyclopropane-3,6Air-1,5Nitrogen-1,4', 'role': 'assistant'}]