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': 'Sinus not present at birth is - \nSelect and explain. \nA. Ethmoid, B. Maxillary, C. Sphenoid, D. Frontal', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Development and grwoth of paransal sinuses', 'role': 'assistant'}]