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': 'Most common sinus involved in acute sinusitis? \nSelect and explain. \nA. Ethmoid, B. Maxillary, C. Sphenoid, D. Frontal', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The sinus most commonly involved is the maxillary followed in turn by ethmoid, frontal and sphenoid. (Ref: Diseases of ENT, PL Dhingra, 7th edition, of no. 213)', 'role': 'assistant'}]