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: Gynaecology & Obstetrics
[{'content': 'Ligamentum teres is formed after \nSelect and explain. \nA. Obliteration of the umbilical vein, B. Obliteration of the ductus venous, C. Obliteration of the ductus arteriosus, D. Obliteration of the hypogastric artery', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Umbilical vein\xa0closure occurs shortly after closure of umbilical arteries and forms the ligamentum teres.', 'role': 'assistant'}]