5. What happens to the blood flow in the cardiac cycle?
A. Blood flows into the aorta through the semilunar valve due to contraction of the right ventricle.
B. Blood flows into the left atrium through the pulmonary artery when the walls of the left atrium
relax.
C. Blood flows into the right atrium through the vena cava when the walls of the right atrium relax.
D. Blood flows into the right ventricle through the semilunar valve when the walls of the right
atrium contract.