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: Anatomy
[{'content': 'All open into middle meatus except ? \nSelect and explain. \nA. Frontal sinus, B. Sphenoid sinus, C. Maxillary sinus, D. Ethmoidal sinus', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Sphenoid sinus Pa of lateral nasal wallOpeningsInferiorNasolacrimal ductMiddleFrontal sinus, Maxillary sinus, Anterior ethmoidal sinusSuperiorPosterior ethmoidal sinusSphenoethmoidal recessSphenoid sinus", 'role': 'assistant'}]