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
Most common sinus to be involved in acute sinusitis? 
Select and explain. 
A. Ethmoid, B. Maxillary, C. Sphenoid, D. Frontal
B: Maxillary
Answer: B: Maxillary 
Explanation: Ans. is 'b' i.e., Maxillary Most common sinus affected by sinusitis overall Maxillary Most common sinus affected in adult Maxillary Most common sinus affected in children Ethmoid Least common sinus affected Sphenoid Sinuses involved in order of frequency Maxillary > Frontal > Ethmoid > Sphenoid