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': 'Features of right side carcinoma colon are\nI. Obstruction\nII. Altered bowel habit\nIII. Anemia\nIV. Melena \nSelect and explain. \nA. 1 only, B. 1 and 2, C. 3 and 4, D. 2, 3 and 4', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Right sided Ca. Bleeds ( melena) causing anemia.', 'role': 'assistant'}]