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
[{'content': 'Which among the following sinuses is most commonly affected in a child - \nSelect and explain. \nA. Sphenoid, B. Frontal, C. Ethmoid, D. Maxillary', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]