Which statement about resting heart rate is true? Increased physical activity and cardiovascular endurance will lower your Resting Heart Rate. Resting heart rate is calculated by subtracting your age from 220. Use your Resting Heart Rate to calculate your Maximal Heart Rate. Your Resting Heart Rate is lowest just before going to bed.

(A) or “Increased physical activity and cardiovascular endurance will lower your Resting Heart Rate

This is because as you continue to train your heart, it becomes more effective in delivering blood. Your RHR will drop due to the bigger bursts of blood your heart is pumping out in which case fewer beats or pumps are needed.
This takes some work load off of the heart and is one of the main reasons why this method of exercise is recommended by Heath professionals.

People who utilizes the progression principle will ensure their exercise program increases in frequency, intensity, time, and type. the changes need to happen gradually in order to ensure they make gains in their fitness program. a person who doesn't utilize the progression principle can still gain health benefits from exercising, but will not continue to improve in cardiovascular fitness.