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: Radiology
[{'content': "Soap bubble appearance is shown by: \nSelect and explain. \nA. Osteoclastoma, B. Osteosarcoma, C. Multiple myeloma, D. Ewing's sarcoma", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]