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: Unknown
[{'content': 'Which of the fontalle is the last to close after birth \nSelect and explain. \nA. Anterior fontanelle, B. Posterior fontanelle, C. Sphenoidal fontanelle, D. Mastoid fontanelle', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ref. The Short Textbook of Pediatrics. Pg 550\n\xa0\n\nAnterior fontanelle closes\xa0 around 10-18 months\nPosterior fontanelle closes around 8 weeks\nPersistent posterior fontanelles is earliest sign of hypothyroidism', 'role': 'assistant'}]