This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anesthesia Machine, Subject name: Anaesthesia
[{'content': 'What is pin index of O2-Co2 (Co2 > 7.5%):- \nSelect and explain. \nA. 1,6, B. 2,6, C. 3,6, D. 4,6', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Gas Index Pins Oxygen 2,5 Nitrous oxide 3,5 Cyclopropane 3,6 O2-CO2 (CO2<7.5%) 2,6 O2-CO2(CO2>7.5%) 1,6 O2-he(He>80.5%) 4,6 O2-he(He<80.5%) 2,4 Air 1,5 Nitrogen 1,4 N2O-O 7', 'role': 'assistant'}]