This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Contracted Pelvis, Subject name: Gynaecology & Obstetrics
[{'content': "Single pelvic ala is present in: \nSelect and explain. \nA. Robert's pelvis, B. Naegele' s pelvis, C. Osteomalacia pelvis, D. Rickets pelvis", 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. B. Naegele's pelvisNaegele's pelvis - Ala on one side is absenta. Robert's pelvis - Ala on both sides are absentb. Osteomalacic pelvis - the shape of inlet is triradiatec. Rachitic pelvis - shape of inlet is reniformd. The expected date of delivery can be calculated by Naegele's rule", 'role': 'assistant'}]