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': 'All are of adult size at bih except? \nSelect and explain. \nA. Mastoid antrum, B. Ear Ossicles, C. Tyrnpanic cavity, D. Maxillary antrum', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The tympanic cavity and mastoid antrum , auditory ossicles and structures of the internal ear are all almost fully developed at bih and subsequently alter little.', 'role': 'assistant'}]