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: Surgery
[{'content': 'Tetanus is caused by - \nSelect and explain. \nA. Cl. Tetani, B. Cl. Welchii, C. Cl. edematiens, D. Cl. Septicum', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]