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 - \nSelect and explain. \nA. Osteosarcoma, B. Osteochondroma, C. Multiple myeloma, D. Osteoclastoma', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Multiple myeloma", 'role': 'assistant'}]