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': 'Spheno-occipital synchondrosis closes at the age of: \nSelect and explain. \nA. 6 years of age, B. Early puberty age, C. Early adult age, D. It never closes', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The spheno-occipital synchondrosis contributes most to growth of the posterior cranial base as it is\xa0the last cranial base suture to ossify. The spheno-occipital synchondrosis closes by 13–15 years of age.\xa0Growth at the spheno-occipital synchondrosis causes elongation of the middle portion of the cranial base as a result of primary displacement, while growth at the posterior part leads to ﬂexion in the\xa0cranial base, since the posterior part of spheno-occipital synchondrosis has a greater amount of bone\xa0formation in its inferior part than its superior part.\nKey Concept:\nAnterior and posterior cranial base lengths increase because of bony deposition, as well\xa0as growth at the spheno-occipital and sphenoethmoidal synchondroses. Postnatally, the posterior\xa0cranial base becomes longer primarily due to growth at the spheno-occipital synchondrosis.\nRef: Orthodontics: Diagnosis and Management of Malocclusion and Dentofacial Deformities 3rd ed pdf\xa0no 654', 'role': 'assistant'}]