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: Pathology
Most common paranasal sinus affected by Osteoma: 
Select and explain. 
A. Frontal sinus, B. Ethmoid sinus, C. Maxillary sinus, D. Sphenoidal sinus
A: Frontal sinus
Answer: A: Frontal sinus 
Explanation: sequence of involvement:
Frontal>ethmoid>Maxillary>sphenoid.