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': 'Abdomino-perineal resection is done in colorectal Ca on the basis of - \nSelect and explain. \nA. Age of patient, B. Distance from anal-verge, C. Fixity of tumor, D. Hepatic metastasis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]