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': 'All of the following are included in first stage of labor except \nSelect and explain. \nA. Effacement of cervix, B. Dilatation of cervix, C. Crowning of fetal head, D. Descent of head', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Crowning is a cardinal movement of labor which occurs during second stage', 'role': 'assistant'}]