This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Medicine
[{'content': '"In pseudomembranous colitis" the investigation of choice is ? \nSelect and explain. \nA. Stool culture, B. CT scan abdomen, C. Glutamate dehydrogenase immunoassay, D. Sigmoidoscopy', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., CT scan abdomen", 'role': 'assistant'}]