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: ENT
[{'content': 'The maxillary sinus opens into middle meatus at the level of - \nSelect and explain. \nA. Hiatus semilunaris, B. Bulla ethmoides, C. Infundibulum, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]