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

Two people are seen playing a game of ping pong with one another. they

Possible answers:
* switch sides constantly and attack one another.
* move around the table with the others watching on the side.
* hit the ball back and fourth across the table while people watch on the sides.
* hit the ball against the wall in front of them.
hit the ball back and fourth across the table while people watch on the sides.