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: Pathology
[{'content': 'Rind sign is seen: \nSelect and explain. \nA. Marfan syndrome., B. Osteopetrosis., C. Fibrous dysplasia., D. All of the above.', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Radiologically the radiolucent lesions in fibrous dysplasia are surrounded by a thick sclerotic border and this is known as rind sign.', 'role': 'assistant'}]