<span>The correct answer is d. increase the rate of breathing.</span> <span> 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.</span>
