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
Posterior ethmoid sinus opens in which meatus? 
Select and explain. 
A. Superior, B. Middle, C. Inferior, D. Spenoethmoidal recess
A: Superior
Answer: A: Superior 
Explanation: Ans. is 'a' i.e., Superior