Pulmonary surfactant serves which of the following functions?

A. It carries fresh oxygen from the lungs to the left side of the heart
B. it dilates the bronchioles in the lungs and enhances the flow of air
C. It lubricates the alveolar walls and allows them to expand and recoil
D. It facilitates the transport of oxygen-poor blood from the right ventricle to the lungs.

Answer: D. It facilitates the transport of oxygen-poor blood from the right ventricle to the lungs.