Thomas knows that he should figure out his resting heart rate to compare it with his heart rate while he is exercising, but he does not know why. What is the BEST way to explain why this is a good idea?
A.
The heart rate is the most important factor in determining fitness.
B.
If his heart rate is too high, he will need to exercise for much longer.
C.
His doctor will ask what his heart rate is when it is time for a check-up.
D.
Monitoring his heart rate will help him find the right intensity of exercise.
