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': 'Which of the following is a dynamic cause of intestinal obstruction: March 2011 \nSelect and explain. \nA. Gall stone, B. Paralytic ileus, C. Mesenteric vascular obstruction, D. Ogilvie syndrome', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. A: Gall stoneGall stone causes dynamic ileus (intraluminal cause)Adynamic cause of intestinal obstruction includes 1) paralytic ileus, 2) mesenteric vascular occlusion and 3) pseudo-obstructOgilvie's syndrome is acute colonic pseudo-obstruction", 'role': 'assistant'}]