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': 'Which of the following bone reaches adult size before birth \nSelect and explain. \nA. Ossicles, B. Mastoid, C. Maxilla, D. Pariental', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The petromastoid part of the neonatal temporal hone encloses the internal ear, middle ear and mastoid antrum, all parts of which are full adult size at birth. But the mastoid process is absent and the stylomastoid foramen is near the lateral surface of the skull.', 'role': 'assistant'}]