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: Anatomy
[{'content': 'Which of the following disappear in umbilical cord \nSelect and explain. \nA. Left aery, B. Left vein, C. Right aery, D. Right aery', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D. i.e. Right vein', 'role': 'assistant'}]