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: Surgery
[{'content': 'BCG used as treatment for which cancer \nSelect and explain. \nA. Lung, B. Bladder, C. Rectum, D. Gall bladder', 'role': 'user'}, {'content': 'Answer: B \nExplanation: BCG is used as intravesical chemotherapeutic agent.', 'role': 'assistant'}]