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: Unknown
[{'content': "'Arrest of labour' is defined as Failure of the head of the fetus to descend within___________. \nSelect and explain. \nA. 1 hour, B. 2 hours, C. 3 hours, D. 4 hours", 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans- B Note- 'Arrest of labor' is defined as Failure of the head of the fetus to descend for 3hours among primiparas and 2 hours among multiparas without an epidural analgesia +1 hour each if epidural analgesia is administered.", 'role': 'assistant'}]