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': 'Safety pin index for oxygen cylinder is? \nSelect and explain. \nA. 2, 5, B. 3,5, C. 1,5, D. 1,4', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., 2, 5 Gas Pin index Oxygen 2,5 Nitrous oxide 3,5 Cyclopropane 3, 6 Air 1, 5 Nitrogen 1, 4 Entonox (50% 02 + 50%N,0) Single central (7) Carbon dioxide (<7.5%) 2, 6 Carbon dioxide (> 7.5%) 1, 6", 'role': 'assistant'}]