<span>The option that best describes their heart rates during this activity is A. low. They aren't doing much at that particluar moment - they are just walking around, talking and laughing. There isn't much there to rise their blood pressure and thus heart rate, which remains low. Moderate, vigorous, and dangerous heart rates would require much more vigorous activities. </span>
Respiratory system is the answer
The answer you are looking for is B.Body type. Any body type can get fit as long as they treat their body right.
Anyways, the answer is cells. Cells in the reproductive organs (testes and ovaries in humans) divide to form gametes.
Hope this helped :)