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
The maxillary sinus opens into middle meatus at the level of: 
Select and explain. 
A. Hiatus semilunaris, B. Bulla ethmoidalis, C. Infundibulum, D. None of the above
A: Hiatus semilunaris
Answer: A: Hiatus semilunaris 
Explanation: The maxillary sinus is the largest of the paranasal sinuses and is located in the maxilla, lateral to the nasal cavity and inferior to the orbit. The maxillary sinus opens into the posterior aspect of the hiatus semilunaris in the middle meatus. The infraorbital nerve (CN V-2) primarily innervates the maxillary sinus.