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
[{'content': 'In the skull all are true except \nSelect and explain. \nA. The sutures are all fibrous joints, B. The coronal suture separates the frontal from the parietal bones, C. The posterior fontanelle usually closes 18 months after birth, D. After middle age cranial sutures begin to ossify from cranial surface', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Posterior fontanelle usually closes between 3rd and 6th months\xa0after birth.', 'role': 'assistant'}]