How can build you muscular endurance?

I would choose A, gradually overload your muscles, also known as progressive overload, the gradual increase of stress placed upon the body during training.

It can't be b because that would build up one's cardiovascular endurance not muscular endurance.

it can't be C although that diet does play a big role when it comes to exercise

and it can't be d because although that helps too it doesn't build muscular endurance.