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': "'Onion Skin' appearance of radiographs is seen in \nSelect and explain. \nA. fibrous dysplasia, B. osteosarcorna, C. Ewing's sarcoma, D. Chondrosarcoma", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]