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': 'Commonest site of Ivory osteoma - \nSelect and explain. \nA. Frontal-Ethmodial region, B. Mandible, C. Maxilla, D. Sphenoid', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ivory osteomas are most commonly seen in frontal sinus followed by ethmoid and maxillary sinus.', 'role': 'assistant'}]