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
The commonest site of obstruction in Gall stone ileus is - 
Select and explain. 
A. Proximal ileum, B. Distal ileum, C. Ileocecal junction, D. Transverse colon
B: Distal ileum
Answer: B: Distal ileum 
Explanation: Ans. is 'b' i.e., Distal ileum