A10 percent increase in the level of carbon dioxide in the blood will select one: a. decrease pulmonary ventilation. b. decrease the alveolar ventilation rate. c. decrease the vital capacity. d. increase the rate of breathing. e. decrease the rate of breathing.

The correct answer is d. increase the rate of breathing.

Peripheral chemoreceptors (the carotid and aortic bodies) can sense hypercapnia (high CO2) and then they send a signal to the breathing centre. Breathing centre is in medulla oblongata which regulates breathing movements. When CO2 reaches a certain level, a signal is sent to trigger an inhalation and the rate of breathing is increased.