Question

the beginning of the respiratory system that warms and moistens the air.
trachea
bronchi
nose
diaphragm

Explanation:

The nose is the starting point of the respiratory system. It has nasal hairs that filter dust, and the nasal mucosa warms and moistens the incoming air. The trachea is just a passageway. The bronchi are branches in the lungs. The diaphragm is a muscle for breathing movement, not for warming and moistening air. So the answer is nose.

Answer:

C. nose