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
[{'content': 'Most common site of gall stone impactation is - \nSelect and explain. \nA. Duedenojejunal junction, B. Proximal to iliocaecal junction, C. Distal to iliocaecal junction, D. Colon', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans is 'b' i.e., Proximal to Ileocaecal junction", 'role': 'assistant'}]