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': 'True about Ca colon - \nSelect and explain. \nA. 1/3rd of cases shows liver metastasis, B. Obstruction common in sigmoid colon, C. CEA is useful for prognostic impoance, D. All', 'role': 'user'}, {'content': "Answer: D \nExplanation: Answer 'a' i.e. 1/3rd of cases shows liver metastases; 'b' i.e. Obstruction common in sigmoid colon 'c' i.e. CEA is useful for prognostic impoance", 'role': 'assistant'}]