What happens to air as it passes through the respiratory structures? A
The air is simply transported to the alveoli by the respiratory structures, while maintaining its temperature.

B
The air undergoes a series of reactions to break the oxygen down so it is more easily diffused in the alveoli.

C
The air is filtered and kept cool so no new pathogens form as it makes its way to the alveoli.

D
The air is warmed, moistened, and filtered so that it is clear of pathogens and can easily diffuse in the alveoli.