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: ENT
Paranasal sinuses present at birth are 
Select and explain. 
A. Frontal and maxillary, B. Ethmoid and maxillary, C. Frontal and ethmoid, D. Sphenoid and ethmoid
B: Ethmoid and maxillary
Answer: B: Ethmoid and maxillary 
Explanation: Paranasal sinuses develop as outpouchings from the mucous membrane of a lateral wall of the nose. 
The growth of sinuses continues during childhood and into early adult life.
Radiologically maxillary sinuses can be identified at 4-5 months, ethmoids at 1 year,  sphenoid at 4 years and frontals at 6 years.