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
Recently according to ACOG and society for maternal-fetal medicine, Active labor is redefined to sta at 
Select and explain. 
A. 3cm, B. 4cm, C. 5cm, D. 6cm
D: 6cm
Answer: D: 6cm 
Explanation: More recently, a consensus committee of ACOG has redefined active labor to begin at 6cm.(Ref: William's Obstetrics; 25th edition)