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
Patchy calcification is the x-ray feature of bone tumor 
Select and explain. 
A. Osteosarcoma, B. Chondroblastoma, C. Fibrous dysplasia, D. Osteoclastoma
B: Chondroblastoma
Answer: B: Chondroblastoma 
Explanation: None