Question

What causes the heart's lub dub sound?

A. capillaries moving blood between arteries and veins
B. arteries delivering oxygen rich blood to the rest of the
body
C. valves opening and closing while returning blood to
the heart
D. lungs oxygenating blood and exhaling carbon dioxide

Answer 1

The answer of this question is the opening and closing of the heart valves of the heart valves. I believe that the answer is C, or "valves opening and closing while returning blood to the heart"