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': 'Investigation of choice for fistula in ano is \nSelect and explain. \nA. MRI, B. Fistulogram, C. MR fistulogram, D. CT scan', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Initial investigation is fistulogram.\nIOC is MR fistulogram.', 'role': 'assistant'}]