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: Pathology
[{'content': "Toxic megacolon is seen as a complication in ? \nSelect and explain. \nA. Crohn's disease, B. Ulcerative colitis, C. Colonic diverticulosis, D. Miliary TB", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Toxic megacolon can arise as a \xa0complication following chronic ulcerative colitis.', 'role': 'assistant'}]