This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
[{'content': 'PO2 over 8kPa is (Hp saturation) \nSelect and explain. \nA. 60%, B. 70%, C. 80%, D. 90%', 'role': 'user'}, {'content': 'Answer: D \nExplanation: PO2 over 8kPa is 90%Ref: Ganong&;s Review of Medical Physiology; 24th edition; page no: 642', 'role': 'assistant'}]