Two friends of different masses are on the playground. they are playing on the seesaw and are able to balance it even though their masses are different.

how are they able to balance on the seesaw?

1) they are able to balance torques due to gravity.
2) they are able to balance their respective energies.
3) all of these.
4) their densities are the same.
5) they are able to balance forces due to gravity.
6) they are able to balance their respective momenta.