If you wish to lower your risk of heart disease, then you should make sure to be physically active, quit smoking if you do, eat healthy foods, lower blood pressure, etc.
In order to calculate your target heart rate, you must figure out your resting heart rate.
So {A} would be the best answer.
Trueeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee
Nervous system is what your ooking for
