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: Gynaecology & Obstetrics
[{'content': "Naegele's pelvis is : \nSelect and explain. \nA. Triradiate pelvis, B. One ala absent, C. Two alae absent, D. None", 'role': 'user'}, {'content': 'Answer: B \nExplanation: One ala absent', 'role': 'assistant'}]