This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Embryology 1, Subject name: Anatomy
[{'content': 'Which of the following does not pass through the primitive umbilical ring? \nSelect and explain. \nA. Allantois, B. Amnion, C. Yolk sac, D. Connecting stalk', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The amnion does not pass through the primitive umbilical ring. As craniocaudal folding occurs, the amnion becomes the outer covering of the umbilical cord.', 'role': 'assistant'}]