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: Microbiology
[{'content': '"Pseudomembranous" colitis is caused by: \nSelect and explain. \nA. Clostridium botulinum spores, B. Clostridium difficile, C. Clostridium perfringens, D. Clostridium tetani', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Clostridium difficile', 'role': 'assistant'}]