This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
[{'content': 'How many weeks after delivery blood volume returns to pre-pregnant levels : \nSelect and explain. \nA. 1 week, B. 2 weeks, C. 4 weeks, D. 6 weeks', 'role': 'user'}, {'content': "Answer: B \nExplanation: Blood volume reaches prepregnant value by 1 week postpaum after delivery Cardiac Output reaches prepregnant value by 10days postpaum after delivery Reference: William's Textbook of Obstetrics 24th edition page no 690", 'role': 'assistant'}]