As the ventricles begin to contract, blood pushes against the av valves and closes them, causing
a. blood to pass into the atria.
b. the second heart sound.
c. the first heart sound.
d. a heart murmur.

C. the first heart sound.

Explanation:

The valves open and close due to undue pressure difference of blood across these valves. The AV or atrioventricular valve separates the atrium from the ventricles on each half of the heart.

The closure of the AV valve will result in the production of the first sound of the heart. The AV valve prevent the back flow of blood to the atria.

answer:

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