Answer:
A
Step-by-step explanation:
The correct answer is A: The heart muscle contracts to reduce the volume in the heart chambers.
When the heart muscle contracts, it creates pressure that pushes blood out of the heart and into the arteries. The contractions are initiated by electrical signals that spread through the heart muscle, causing the heart muscles to contract in a coordinated manner. During the contraction, the ventricles (the two lower chambers of the heart) reduce in volume, which forces blood out of the heart and into the blood vessels. This process is known as systole.
After the heart has pushed the blood out, it relaxes to allow the blood to fill the heart again. During this relaxation phase, known as diastole, the heart chambers increase in volume, allowing blood to flow in from the veins. This cycle of contraction and relaxation allows the heart to pump blood efficiently and effectively throughout the body.