This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharyngeal arch and its derivatives, pharyngeal arch aeries, Subject name: Anatomy
[{'content': 'The structure marked A begins to close by what time frame and due to what cause? \nSelect and explain. \nA. Begins to close at 10-15 hours after bih, due to withdrawal of prostaglandins, B. Begins to close at 10-15 hours after bih, due to expression of prostaglandins, C. Begins to close 4 weeks after bih, due to fall in oxygen concentration, D. Begins to close 4 weeks after bih, due to rise in oxygen tension', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The structure marked is ductus aeriosus which begins to close 10-15 hours after bih due to withdrawal of prostaglandins and exhibits functional closure by 7 days and anatomical closure by 4 weeks after bih.', 'role': 'assistant'}]