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
The most common bone tumor that occurs in children is: 
Select and explain. 
A. Osteosarcoma, B. Ewing's sarcoma, C. Metastatic carcinoma, D. Multiple myeloma
A: Osteosarcoma
Answer: A: Osteosarcoma 
Explanation: None