This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Mastoid fontanelle closes by \nSelect and explain. \nA. 1-3 months, B. 3-6 months, C. 11-12 months, D. 18-24 months', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Closure of Fontanelles:1. Anterior fontanelle by 18 months2. Posterior fontanelle by 2-3 months3. Sphenoidal fontanelle by 2-3 months and 4. Mastoid fontanelle by 12 months Reference: Chourasia; 6th edition; 12th page', 'role': 'assistant'}]