The Nurse Recognizes That a Rising Level of Partial Pressure

The nurse recognizes that a rising level of partial pressure of carbon dioxide (CO?) in arterial blood (PaCO?) in a patient with COPD means that:

A) More arterial O? is available than is needed.
B) The ventilation-perfusion ratio is becoming balanced.
C) Respiratory acidosis has begun.
D) The anticholinergic medications are effective.