A 36-year-old man visits his doctor because his wife has long complained of his snoring, but recently observed that his breathing stops for a couple of minutes at a time while he is sleeping. He undergoes polysomnography and ventilatory response testing to ascertain the extent and cause of his sleep apnea. The activity of the central chemoreceptors is stimulated by which of the following?
a. A decrease in the metabolic rate of the surrounding brain tissue
b. A decrease in the PO₂ of blood flowing through the brain
c. An increase in the PCO₂ of blood flowing through the brain
d. An increase in the pH of the CSF
e. Hypoxemia, hypercapnia, and metabolic acidosis