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 characteristic radiological feature of fibrous dysplasia - \nSelect and explain. \nA. Thickened bone matrix, B. Cortical erosion, C. Ground glass appearance, D. Bone enlargement', 'role': 'user'}, {'content': 'Answer: C \nExplanation: In long bones, the fibrous dysplastic lesions are typically well-defined, radiolucent areas with thin cortices and, a ground-glass appearance. The articular ends are usually spared.', 'role': 'assistant'}]