What happens next in this paragraph?

An elderly man is using an elliptical trainer inside a gym. he
Choose from:
[A]. uses it to walk against the wall.;
[B]. walks to and fro, trying to exercise inside while also using the elliptical trainer.;
[C]. is using it to walk, speed, and perform various way to flip.;
[D]. pedals and pushes back and forth as he talks to the person with the camera.;
[D].