Which of these structures appears radiopaque?
Radiopaque refers to that portion of the radiograph that appears light or white. Radiopaque structures are dense and absorb or resist the passage of the X-ray beam, E.g., Enamel, dentin and bone.
Nasal septum
On the panoramic radiograph, it appears as a vertical radiopaque partition that divides the nasal cavity.
Reference: Freny R Karjodkar Oral Radiology Principles and Interpretation 2nd  edition page no 251
Maxillary sinus
Nasal fossa
Nasal septum
Mental foramen