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': 'Nagler reaction is shown by: \nSelect and explain. \nA. Cl. difficle, B. Cl. perfringens, C. Cl. tetani, D. Cl. butryicum', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is. b' i. e. Cl. perfringens", 'role': 'assistant'}]