Multi-select problem: How does the next paragraph end?

We see small kids ride bmx bikes on a dirt track in an arena. The kids ride past the camera. the kids

Choices:
[I] stop a while and walk the grassy area of the arena.;
[II] start passing the finish line.;
[III] play on a dirt track.;
[IV] continue to ride in their dirt bikes.;
[II]