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: Surgery
[{'content': 'Most common site of gall stone impaction is \nSelect and explain. \nA. Duodeno-jejunal junction, B. Proximal to ileocaecal junction, C. Distal to ileocaecal junction, D. Colon', 'role': 'user'}, {'content': "Answer: B \nExplanation: Gall stone ileus It is an acute intestinal obstruction, often seen in elderly and is due to Blockage be a bolus or mass of gallstones which commonly enter the intestines through cholecystoduodenal fistula (75%) or rarely through cholecystointestinal or gastric fistula MC site : Between gallbladder and duodenum 2nd MC site : Between gallbladder and transverse colon Obstruction is seen in Distal ileum or proximal to ileocaecal junction Ref: SRB's Manual of Surgery 5th edition Pgno : 648", 'role': 'assistant'}]