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: Microbiology
[{'content': "Most common tumor associated with AIDS is \nSelect and explain. \nA. Carcinoma, B. Kaposi's sarcoma, C. Melanoma, D. Ewing's sarcoma", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]