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: Orthopaedics
[{'content': 'A patient of nephrotic syndrome taking steroids for 6 years presented with a limping gait and of limitation of abduction and internal rotation. He most probably has - \nSelect and explain. \nA. Primary osteoarthritis, B. Avascular necrosis, C. Tuberculosis, D. Aluminum toxicity', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]