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
Maxillary sinus achieves maximum size at: 
Select and explain. 
A. At bih, B. At primary dentition, C. At secondary dentition, D. At pubey
C: At secondary dentition
Answer: C: At secondary dentition 
Explanation: Maxillary sinus is the first sinus to develop at bih.It is completely developed by 9 years of age, i.e. approximately at the time of secondary dentition.