Spaces in the bones of the head that connect to the nose passage.

• A. Nasal mucous membrane
• B. Sinus cavities
• C. EEG
• D. Refractive errors

Answer: (B)

The spaces inside the skull bones that connect to the nasal passages are the sinus cavities. These are air-filled chambers in areas like the forehead, cheeks, between the eyes, and behind the nose, and they drain into the nasal cavity through small openings. They’re lined with a nasal mucous membrane and serve roles such as humidifying and warming inhaled air, producing mucus, reducing skull weight, and helping with voice resonance. The nasal mucous membrane is the lining, not the empty spaces themselves. EEG measures brain electrical activity, and refractive errors relate to how the eye focuses light, not skull anatomy.