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': 'Ludwig angina is usually caused by \nSelect and explain. \nA. Streptococci and various mixed anaerobes, B. Anaerobic\tinfection\tby\tprevotella\tand fusobacterium, C. Paramyxovirus, D. Candida species', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]