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': 'Investigation of choice for colon cancer is \nSelect and explain. \nA. CECT, B. Barium enema, C. Barium swallow, D. Colonoscopy', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Colonoscopy is for Ca. Colon.', 'role': 'assistant'}]