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': 'Most common cause of primary lung abscess is: \nSelect and explain. \nA. Aerobic bacteria, B. Anaerobic bacteria, C. Acid fast bacteria, D. Dimorphic fungal infection', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Most common cause of primary lung abscess is by anaerobic bacteria, usually caused by aspiration of organisms for oropharynx.', 'role': 'assistant'}]