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 index for Air is \nSelect and explain. \nA. 1,4, B. 2,5, C. 5, D. 1,5', 'role': 'user'}, {'content': 'Answer: D \nExplanation: PIN index number prevents wrong fitting of the cylinders . AIR - 1 ,5 02 - 2 ,5 N20 - 3 ,5 CO2 - 1 ,6 ; 2,6(Liquid) Cyclopropane 3 ,6 Entonox 7', 'role': 'assistant'}]