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': 'Involution of uterus takes -- weeks : \nSelect and explain. \nA. 4, B. 6, C. 12, D. 20', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 6', 'role': 'assistant'}]