Why does your heart rate increase while exercising?

I'd myself say it's because a lot of people are fat but here's the real answer ;)

During exercise, your body may need three or four times your normal cardiac output, because your muscles need more oxygen when you exert yourself. During exercise, your heart typically beats faster so that more blood gets out to your body.

the correct answer is option d

explanation:

i was wrong its d because they dont use cm when calculating square roots

d.) circle motion requires a force to give it a centripetal acceleration.