George's highest target heart rate is 170. Yesterday on the stair stepper machine, his heart rate went to 172. What should he do the next time he uses this machine to get the most effective workout?
A.) Use the settings of the machine to increase the intensity.
B.) Use the settings of the machine to decrease the intensity.
C.) Use a workout app to calculate a longer workout duration.
D.) Use a workout app to calculate a shorter workout duration.