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
[{'content': 'Age of closure of spheno-occipital synchondrosis: \nSelect and explain. \nA. 6 years, B. 12 years, C. 18 years, D. 25 years', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Postnatally, the posterior cranial base becomes longer primarily due to growth at the\xa0spheno-occipital synchondrosis. Histologic studies have shown\xa0that the spheno-occipital synchondrosis fuses at approximately\xa016 to 17 years in females and 18 to 19 years in males.\nRef: Graber LW, Vanarsdall RL, Vig KW, Huang GJ. Orthodontics: current principles and techniques. Edition 6 page no 10', 'role': 'assistant'}]