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 is termed according to its internal opening present with reference to - 
Select and explain. 
A. Anal canal, B. Dentate line, C. Anorectal ring, D. Sacral promontory
C: Anorectal ring
Answer: C: Anorectal ring 
Explanation: None