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': 'To diagnose prolonged latent phase in a nulliparous women, latent phase should be prolonged for \nSelect and explain. \nA. > 6 hours, B. > 10 hours, C. > 14 hours, D. > 20 hours', 'role': 'user'}, {'content': "Answer: D \nExplanation: ParityProlonged latent phaseNulliparous> 20 hoursMultiparous> 14 hoursReference: William's Obstetrics; 25th edition; Chapter 23; Abnormal Labor", 'role': 'assistant'}]