What is the primary function of the upper respiratory system?
a)to move air toward the lungs while warming, moistening, and filtering it
b) to diffuse oxygen and carbon dioxide in and out of the cells
c) to absorb and break down nutrients after they are consumed
d) to pad the head with the air pockets to protect against brain trauma.

a)to move air toward the lungs while warming, moistening, and filtering it

Explanation:

The respiratory system consists of the upper and lower respiratory tract (airways). The upper respiratory tract consists of organs located outside the rib cage: external nose, nasal cavity, pharynx, larynx and upper trachea. These organs are responsible for the entry of oxygen into the body, so we can say that the function of the upper respiratory system is to move the air in the environment towards the lungs while heating, moistening and filtering.