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: Dental
Age of closure of spheno-occipital synchondrosis: 
Select and explain. 
A. 6 years, B. 12 years, C. 18 years, D. 25 years
C: 18 years
Answer: C: 18 years 
Explanation: Postnatally, the posterior cranial base becomes longer primarily due to growth at the spheno-occipital synchondrosis. Histologic studies have shown that the spheno-occipital synchondrosis fuses at approximately 16 to 17 years in females and 18 to 19 years in males.
Ref: Graber LW, Vanarsdall RL, Vig KW, Huang GJ. Orthodontics: current principles and techniques. Edition 6 page no 10