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
All are of adult size at birth except- 
Select and explain. 
A. Mastoid antrum, B. Ear ossicles, C. Tympanic cavity, D. Maxillary antrum & orbit
D: Maxillary antrum & orbit
Answer: D: Maxillary antrum & orbit 
Explanation: None