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
High or low fistula in ano are divided by which of the following 
Select and explain. 
A. Anorectal ring, B. Anal canal, C. External anal spincter, D. Dentate line
A: Anorectal ring
Answer: A: Anorectal ring 
Explanation: Anorectal ring is formed by internal anal spincter, external anal spincter and puborectalis muscle.