PaCO2 changes rapidly while HCO3- changes more slowly because PaCO2 is controlled by the lungs while HCO3- is regulated by the kidneys. Which statement best describes this?

• A. PaCO2 changes rapidly; HCO3- changes more slowly; PaCO2 is controlled by the lungs while HCO3- is regulated by the kidneys.
• B. HCO3- changes rapidly; PaCO2 changes more slowly; HCO3- is regulated by the kidneys.
• C. Both PaCO2 and HCO3- change at the same rate, controlled by lungs.
• D. PaCO2 changes slowly and is regulated by kidneys; HCO3- changes rapidly and is regulated by lungs.

Answer: (A)