This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrine System, Subject name: Physiology
Oxygen saturation of blood in the umbilical aery is about: 
Select and explain. 
A. 40%, B. 60%, C. 75%, D. 97%
B: 60%
Answer: B: 60% 
Explanation: PO2 Hb saturation (%) Umbilical aery 23 60 Umbilical vein 30 85