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': 'Ligamentum arteriosum is a remnant of \nSelect and explain. \nA. Ductur arteriosur, B. Ductur caroticus, C. Ductur venosus, D. None', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]