The job of the human heart is to circulate blood through all of the body's arteries, capillaries, and veins. The job of the human lungs is to supply the small amount of blood in them with oxygen. The interaction of these two parts of the human body results in a system that A. removes old blood from the body. B. circulates oxygen-filled blood throughout the body. C. turns the protein in blood into food energy for the digestive system. D. breaks down food energy, and turns it into heat.