This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Bio-Chemistry), Subject name: Biochemistry
[{'content': 'PIN number of oxygen is \nSelect and explain. \nA. 2,5, B. 3,5, C. 2,6, D. 3,6', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: a (2,5 ) Ref: Ajay Yadov, 2nded, p. 22Pin index for gasesOxygen-2,5 Entonox(50%02 +50%N2O)-7Nitrous oxide-3,5 Carbondioxide(<7.5%)-2,6Cyclopropane-3,6 Carbondioxide(> 7.5%)-1,6Air-1,5 Nitrogen-1,4', 'role': 'assistant'}]