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: Anatomy
[{'content': 'The maxillary air sinus opens into middle meatus at: \nSelect and explain. \nA. Infundibulum, B. Summit of infundibulum, C. Bulla ethmoidalis, D. Hiatus semilunaris', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]