Question

serves as an airway and is continuous with the nasal cavity
hilum
conducting zone
nasopharynx

Explanation:

The nasopharynx is part of the upper - respiratory tract. It serves as an airway and is continuous with the nasal cavity. The hilum is related to the root of an organ like the lung and has no relation to the nasal - cavity continuity. The conducting zone is a more general term for parts of the respiratory system that move air, but the specific structure continuous with the nasal cavity is the nasopharynx.

Answer:

Nasopharynx