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: Pharmacology
[{'content': 'Pin index of oxygen is which one of the following : \nSelect and explain. \nA. 2, 5, B. 3, 5, C. 1, 5, D. 3, 6', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]