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': 'Most common primary malignant bone tumor is: \nSelect and explain. \nA. Osteosarcoma, B. Ewing sarcoma, C. Metastatic carcinoma, D. Multiple MyeLoma', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]