This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal Radiology, Subject name: Radiology
[{'content': 'Saw tooth appearance on barium study is seen in \nSelect and explain. \nA. Intussusception, B. Ileocecal TB, C. Ischemic colitis, D. Diveiculosis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Diveiculosis Saw-tooth appearance to the colon, usually sigmoid, with shoening of the bowel, crowding of haustra and picket-fencing of folds Ischemic colitis - thumb printing sign.', 'role': 'assistant'}]