This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Skeletal system, Subject name: Radiology
Onion - peel appearance is seen in - 
Select and explain. 
A. Ewing's sarcoma, B. Osteoma, C. Osteosarcoma, D. Osteoclastoma
A: Ewing's sarcoma
Answer: A: Ewing's sarcoma 
Explanation: Onion peel periosteal reaction is seen in Ewings sarcoma.