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 enterocolitis is caused by: \nSelect and explain. \nA. Cl. perfringens, B. Cl. welchii, C. Cl. difficile, D. Pseudomonas', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Cl. difficile', 'role': 'assistant'}]