Question

how does the heart pump blood?
o the right side of the heart contracts then the left side of the heart, followed by relaxation of the entire heart.
o each chamber contracts independently of the other chambers.
o all four chambers contract at the same time.
o the atria contract, then the ventricles, followed by relaxation of all four chambers.

Explanation:

The cardiac cycle involves the atria contracting first (atrial systole) to push blood into the ventricles. Then the ventricles contract (ventricular systole) to pump blood out of the heart. After that, all four chambers relax (diastole) to fill with blood again.

Answer:

The atria contract, then the ventricles, followed by relaxation of all four chambers.