The answer is; graph A
Breathing increases during exercise because the body is demanding more oxygen for the muscles. The hypothalamus detects the increased carbon dioxide in the blood dur9ng exercise and its commands the lungs to breath faster and deeper. When exercise stops, the body is restored to resting through homeostasis.
The correct answer is: 3.A
During the exercise, heartbeat and breathing rates increase. The heart must increase its rate of pumping in order to deliver oxygen to the muscles faster. The demand for the oxygen increase, the lungs must work harder and the breathing rate increases. As a result, more carbon dioxide is produced and it needs to be removed.