You Placed a Person in an Air-Tight Chamber with a Treadmill

Multiple Choice

You placed a person in an air-tight chamber with a treadmill set at first and comfortable walking speed, but then gradually inclined so that to maintain the same speed, walking intensity had to increase. At this point, then, if the ambient levels of carbon dioxide was gradually raised to levels that are just high enough to raise its levels in the blood, but not enough to cause unconsciousness or kill the person, what would be the probable resulting respiratory rate?

A) It would not change.
B) It would gradually increase throughout the duration of the experiment.
C) It would gradually decrease throughout the duration of the experiment.
D) it would increase and then gradually decrease as carbon dioxide levels rose.
E) It would decrease and then gradually increase as carbon dioxide levels rose.