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': 'All of the following are known complications of ulcerative colitis except : \nSelect and explain. \nA. Stricture, B. Perforation, C. Toxic megacolon, D. Carcinoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: • Inflammation is purely mucosal in ulcerative colitis, strictures are highly uncommon. Any stricture diagnosed in a patient with ulcerative colitis is presumed to be malignant until proven otherwise.', 'role': 'assistant'}]