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What is the lub-dub sound of a heartbeat? blood moving through the arteries and veins pacemaker controlling the heart rate atria contracting followed by the ventricles valves of the heart closing

User Paulwhit
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Answer:

D. valves of the heart closing

Step-by-step explanation:

User Sahin Erbay
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Atria contracting followed by the ventricles' valves of the heart closing

User Terry Harvey
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