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': 'Dukes classification is used for ? \nSelect and explain. \nA. Pancreas carcinoma, B. Gastric carcinoma, C. Urinary bladder carcinoma, D. Colo-rectal carcinoma', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Colo-rectal carcinoma", 'role': 'assistant'}]