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': 'Which is the most common primary malignant bone tumor? \nSelect and explain. \nA. Osteosarcoma, B. Osteoclastoma, C. Secondaries, D. Multiple myeloma', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Secondaries are the most common malignant bone tumor. But the most common primary malignant bone tumor is\xa0Multiple myeloma..', 'role': 'assistant'}]