This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Gynaecology & Obstetrics
[{'content': 'Recently according to ACOG and society for maternal-fetal medicine, Active labor is redefined to sta at \nSelect and explain. \nA. 3cm, B. 4cm, C. 5cm, D. 6cm', 'role': 'user'}, {'content': "Answer: D \nExplanation: More recently, a consensus committee of ACOG has redefined active labor to begin at 6cm.(Ref: William's Obstetrics; 25th edition)", 'role': 'assistant'}]