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2 votes
Your heart rate increases when exercising because:

a. your muscle cells need more oxygen
b. your muscle cells start growing faster
c. your heart creates more blood
d. your heart sends more blood to the muscle cells

1 Answer

4 votes
Answer: D
Explanation: During exercise, the humans body needs more oxygen than the normal cardiac output, because your muscles are needing it. The heart beats faster to get more blood to your body.
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