This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Multiple Myeloma, Subject name: Orthopaedics
[{'content': 'Most common primary malignancy of bone is? \nSelect and explain. \nA. Multiple myeloma, B. Osteoid osteoma, C. Osteosarcoma, D. PNET', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. (a) Multiple myelomaRef.'.Apley's 8/e, p 191)", 'role': 'assistant'}]