What happens next in this paragraph?

A bunch of people are inside a dimly lit gym. They are riding recumbent bikes while being led. they
Available options:
(1). start doing sit ups as they do their exercise.;
(2). ride around the track and participate in several competitions.;
(3). alternate bumping into each other as they go on.;
(4). clap their hands and pedal quickly.;
(4).