Which of the following statements concerning the cardiovascular system is true?
A. The subclavian arteries supply blood to the pelvis and legs.
B. The heart is a muscular organ located behind and to the right of the sternum.
C. It consists of four major components: the heart, the lungs, the blood vessels, and blood.
D. An electrical impulse that starts in the right atrium stimulates contraction of the heart muscle.