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: Anatomy
[{'content': 'Uteroplacental blood flow at term is : \nSelect and explain. \nA. 300-500 ml/min, B. 500-700 ml/min, C. 700-900 ml/min, D. 900-1100 ml/min', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Using ultrasound to study the uterine aeries, uteroplacental blood flow has been measured to increase progressively during pregnancy from approximately 450 ml/min in mid trimester to nearly 500-700 ml/min at 36 weeks. Ref: Williams Obs 25 e pg 132.', 'role': 'assistant'}]