Retta wants to take some of her exercises that build muscular strength and convert

Retta wants to take some of her exercises that build muscular strength and convert them to help her also build muscular endurance. What is the EASIEST way for her to convert these exercises to reach this goal?
ОА She should add range of motion to her exercises.
OB. She should add more stretching to her exercises.
OC. She should add heavier weights to her exercises.
OD
She should add more repetition to her exercises.