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
[{'content': 'Oxygen saturation of blood in the umbilical aery is about: \nSelect and explain. \nA. 40%, B. 60%, C. 75%, D. 97%', 'role': 'user'}, {'content': 'Answer: B \nExplanation: PO2 Hb saturation (%) Umbilical aery 23 60 Umbilical vein 30 85', 'role': 'assistant'}]