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
A characteristic radiological feature of fibrous dysplasia - 
Select and explain. 
A. Thickened bone matrix, B. Cortical erosion, C. Ground glass appearance, D. Bone enlargement
C: Ground glass appearance
Answer: C: Ground glass appearance 
Explanation: 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.