This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Anatomy
[{'content': 'In gallstone ileus, obstruction is seen at \nSelect and explain. \nA. Jejunum, B. Proximal ileum, C. Distal ileum, D. Colon', 'role': 'user'}, {'content': "Answer: C \nExplanation: Gallstone ileus Passge of stone through a spontaneous biliary-enteric fistula leading to a mechanical bowel obstruction Most common site of fistula : Between the gallbladder and duodenum Clinical features Rigler's triad - Classic pain abdominal film triad of small bowel obstruction, pneunobilia & ectopic gallstone is considered pathognomic Most common site of obstruction is ileum(60%); jejunum (15%); colon(5%> sigmoid colon) & duodenum (5%) Ref:1506-1507", 'role': 'assistant'}]