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
Investigation of choice for fistula in ano is 
Select and explain. 
A. MRI, B. Fistulogram, C. MR fistulogram, D. CT scan
C: MR fistulogram
Answer: C: MR fistulogram 
Explanation: Initial investigation is fistulogram.
IOC is MR fistulogram.