This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pediatrics
[{'content': 'Anatomical closure of ductus aeriosus occurs at ________ \nSelect and explain. \nA. Bih, B. 3-4 days, C. 10-21 days, D. 10-15 hours', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ductus aeriosus is functionally closed at 10-15 hours after bih and then anatomical closure occurs at 10-12 days. Ref: Ghai essential pediatrics 9th edition Pgno: 400', 'role': 'assistant'}]