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

Multiple Choice

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.
-Draw a graph that shows a relationship between carbon dioxide and yawning that supports the hypothesis of the scientists. To graph their results, the scientists would plot the ________.

A) number of yawns on the x-axis
B) dependent variable on the x-axis
C) level of carbon dioxide on the x-axis
D) age of college students on the x-axis