Question

is/are to lower respiratory system; ________ is/are to upper respiratory system. nose; lungs lungs; trachea lungs; mouth nose; mouth

Explanation:

The upper respiratory system includes the nose and mouth which are the entry - points for air. The lower respiratory system contains the lungs where gas exchange occurs. The trachea is part of the lower respiratory system but not the best - fit for the upper respiratory system in this context.

Answer:

C. Lungs; mouth