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
[{'content': 'Paranasal sinuses present at birth are \nSelect and explain. \nA. Frontal and maxillary, B. Ethmoid and maxillary, C. Frontal and ethmoid, D. Sphenoid and ethmoid', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Paranasal sinuses develop as outpouchings from the mucous membrane of a lateral wall of the nose. \nThe growth of sinuses continues during childhood and into early adult life.\nRadiologically maxillary sinuses can be identified at 4-5 months, ethmoids at 1 year,\xa0 sphenoid at 4 years and frontals at 6 years.', 'role': 'assistant'}]