This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infection, Subject name: Medicine
[{'content': 'Most common cause of surgical wound infection is: \nSelect and explain. \nA. Staph aureus, B. Streptococcus, C. Pseudomonas, D. Anaerobes', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: aRef: Harrison, 16thed, p. 778', 'role': 'assistant'}]