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
Sentinel pile indicates - 
Select and explain. 
A. Carcinoma rectum, B. Internal haemorrhoids, C. Perianal fistula, D. Anal fissure
D: Anal fissure
Answer: D: Anal fissure 
Explanation: None