This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anatomy
[{'content': 'All developed up to the adult size at bih except \nSelect and explain. \nA. Mastoid Antrum, B. Tympanic cavity, C. Orbital cavity, D. Ear ossicle', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Tympanic cavity, mastoid (tympanic) antrum, ear ossicles and the Internal ear are of adult size in the foetal skull.', 'role': 'assistant'}]