Unlike Inspiration, Expiration Is a Passive Act Because No Muscular

Unlike inspiration, expiration is a passive act because no muscular contractions are involved. Expiration, however, depends on two factors. Which of the choices below lists those two factors?

A) the expansion of respiratory muscles that were contracted during inspiration and the lack of surface tension on the alveolar wall
B) the negative feedback of expansion fibers used during inspiration and the outward pull of surface tension due to surfactant
C) combined amount of CO₂ in the blood and air in the alveoli
D) the recoil of elastic fibers that were stretched during inspiration and the inward pull of surface tension due to the film of alveolar fluid