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: Unknown
[{'content': 'Incidence of mucocele is lowest in \nSelect and explain. \nA. Frontal sinus, B. Sphenoid sinus, C. Maxillary sinus, D. Ethmoid sinus', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Paranasal sinus mucocelesmost commonly occur in the third or fourth decades of life with a slight male predilection.\nThe frontal sinus is most commonly affected followed by the ethmoid sinuses, with reports suggesting 70–90 % of mucoceles occur in these locations.\nTen percent of mucoceles occur in the maxillary sinus and the sphenoid sinus is involved rarely', 'role': 'assistant'}]