<span>The question is asking what you can do, if you are earobically fit. These are the options:
A. run a marathon without experiencing fatigue. - this is not possible. Even the most experience marathon runners experience fatigue, as marathons are very extreme activities
B. quit your normal exercise routine without any negative effects. - this is also not true. Being aerobically fit does not stay for life, but you have to practice it, so you have to keep your routine.
C. sustain a regular routine of exercise for 30-60 minutes with minimal fatigue. - yes, this is the correct option! This is doable i you're fit, but not if you're note.
D. lift very heavy weights without injuries to your joints. - this is not true- lifitng heavy weights is always a strain on your body, whether you're fit, or not</span>
Answer:
Holding a stretch for a current amount of time.
Explanation:
<u>d) observing how the heart contracts to pump blood
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