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': "Toxic megacolon is a known complication of - \nSelect and explain. \nA. Pseudomembranous colitis, B. Ulcerative colitis, C. Amebic colitis, D. Hirschprung's disease", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]