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': 'Sentinel pile indicates - \nSelect and explain. \nA. Carcinoma rectum, B. Internal haemorrhoids, C. Perianal fistula, D. Anal fissure', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]