Which stimulates an increased respiratory rate?

Question

A. rebreathing, B. rapid breathing, C. breath holding. More than one answer is possible.

Answer 1

Respiratory rate is increased when carbon dioxide increases in the blood.
Therefore, B would NOT. As this would lower CO2, and thus lower the respiratory rate.
C WOULD. As this would increase CO2, and thus increase respiratory rate.
A, I suppose, depends on the quality of the rebreather. But, theoretically, I believe it would not change the respiratory rate at all...if it removes CO2 efficiently.

So, I say C is your answer.