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
The maxillary air sinus opens into middle meatus at: 
Select and explain. 
A. Infundibulum, B. Summit of infundibulum, C. Bulla ethmoidalis, D. Hiatus semilunaris
D: Hiatus semilunaris
Answer: D: Hiatus semilunaris 
Explanation: None