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
In a 27 yr old male most common cause of a colovesical fistula would be - 
Select and explain. 
A. Crohns disease, B. Ulcerative colitis, C. TB, D. Cancer colon
A: Crohns disease
Answer: A: Crohns disease 
Explanation: None