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': 'Each of the following can cause food poisoning except: \nSelect and explain. \nA. Cl. difficile, B. Staphylococcus, C. Cl. welchii, D. Cl botulinum', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]