<prompt> 59-year-old man has difficulty in breathing through his nose. On examination, his physician finds that he has swelling of mucous membranes of the superior nasal meatus. Which opening of the paranasal sinuses is most likely plugged?Middle ethmoidal sinusMaxillary sinusAnterior ethmoidal sinusPosterior ethmoidal sinus  <response>: Posterior ethmoidal sinus opens into the superior nasal meatus. Maxillary, frontal, and anterior and middle ethmoidal sinuses drain into middle nasal meatus. 