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': '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: Safety pin index cylinder for oxygen is 2 , 5 . It is done to prevent wrong fitting of cylinders .', 'role': 'assistant'}]