Which of the Following Mechanisms Is Responsible for Maintaining a Normal

Which of the following mechanisms is responsible for maintaining a normal PaCO₂ near 40 mm Hg during heavy exercise?

A) $\dot{v}$ A normally increases such that it eliminates CO₂ at a rate proportional to its production.
B) $\dot{v}$ A normally increases such that it increases O₂ at a rate proportional to CO₂ production.
C) $\dot{v}$ A normally increases such that it eliminates CO₂ without increasing its production.
D) $\dot{v}$ A normally remains stable such that CO₂ elimination is proportional to its production.