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: Pathology
Fistula is most common in - 
Select and explain. 
A. Crohn's disease, B. Ulcerative colitis, C. Infective entero colitis, D. Coeliac sprue
A: Crohn's disease
Answer: A: Crohn's disease 
Explanation: None