Multi-choice problem: Continue writing the next sentence in this paragraph:

A man sitting on an exercise equipment. He put his feet on a holder, and put the strap on. he

Options are:
(a). pull the bar, at the same time pushed his legs.;
(b). then slip off the harness, lifting his feet off the bike.;
(c). started to move it back and forth.;
(d). began walking down a track.;
(a).