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: Medicine
[{'content': 'Crepitus in a wound is produced by - \nSelect and explain. \nA. Staph aureus, B. Clostridium tetani, C. Clostridium welchii, D. Pseudomonas', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]