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': 'Most malignant carcinoma of the bladder is - \nSelect and explain. \nA. Malignant vinous tumour, B. Solid tumour, C. Carcinomatous ulcer, D. Adenocarcinoma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Muscle Invasive tumor nearly always solid.', 'role': 'assistant'}]