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
PO2 over 8kPa is (Hp saturation) 
Select and explain. 
A. 60%, B. 70%, C. 80%, D. 90%
D: 90%
Answer: D: 90% 
Explanation: PO2 over 8kPa is 90%Ref: Ganong&;s Review of Medical Physiology; 24th edition; page no: 642