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 site of sinusitis in children \nSelect and explain. \nA. Maxillary sinus, B. Ethmoidal sinus, C. Frontal sinus, D. Spenoid sinus', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Acute ethmoid sinusitis Aetiology Acute ethmoiditis is often associated with infection of other sinuses. Ethmoid sinuses are more often involved in infants and young children. (Ref: Diseases of ENT, PL Dhingra, 7th edition, of no. 216)', 'role': 'assistant'}]