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
The structure marked A begins to close by what time frame and due to what cause? 
Select and explain. 
A. 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
A: Begins to close at 10-15 hours after bih, due to withdrawal of prostaglandins
Answer: A: Begins to close at 10-15 hours after bih, due to withdrawal of prostaglandins 
Explanation: 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.