This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdominal Radiography, Subject name: Radiology
[{'content': "Cobble stoning of intestine with string sign of lean tor is seen in: \nSelect and explain. \nA. Crohn's disease, B. Ulcerative colitis, C. Ischemic colitis, D. Amoebic colitis", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. (a) Crohn's disease* Cobble stone mucosa is appearance of the intestinal mucosa in Crohn's disease to the endoscopist,. Cobblestoning refers to the uniform nodules-due to the sub-mucosal fibrosis.* String sign of Kantor is due to involvement of the terminal ileum in Crohn's disease.* It is caused by severe spasm due to irritability of the loop producing the appearance of a frayed cotton string.* Subsequently the wall of the ileum may become fibrotic and the lumen fixed in diameter.", 'role': 'assistant'}]