This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and paranasal sinuses, Subject name: ENT
[{'content': 'Paranasal sinus present at bih among the following? \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: Maxillary sinus - Develop at bih; completely develop at 9 yearsEthmoidal sinus - Development at bih; completely develop at late pubeyFrontal sinus - Develop at 2 years; completely develop at late adolescenceSphenoid sinus - Develop at 3-5 years; completely develop at 12-15 yearsRef: PL Dhingra, Diseases of Ear, Nose & Throat, 7th edition, pg no. 211', 'role': 'assistant'}]