Scenario Yawning Is a Reflexive Action That Is Often Associated with with Sleepiness

Scenario
Yawning is a reflexive action that is often associated with sleepiness. When a person yawns, the mouth opens, and a longer than normal breath of air is inhaled, followed by a longer than normal exhalation. Hypothesizing that yawning has a regulatory mechanism similar to breathing, scientists conducted an experiment on college students to test the effect of existing carbon dioxide levels on yawning.
-Yawning uses the same muscles as regular breathing. When a person exhales to complete a yawn, what happens?

A) The rib muscles contract.
B) The diaphragm contracts.
C) The rib muscles act in the same way that they do in an inhalation.
D) The diaphragm relaxes.