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 pneumatisation process in maxillary sinus completes in? 
Select and explain. 
A. 6-8 years, B. 13-14 years, C. 8-10 years, D. 18-20 years
D: 18-20 years
Answer: D: 18-20 years 
Explanation: None