Which is an example of observational learning?

Tristan is sure he'll get caught if he sneaks TV time while his mom is out shopping, so he decides not to do it.
Kanu hears a song on the radio and buys the CD so she can play it repeatedly.
Trey plays with his sisters in the backyard, and he swings from a rope ladder to pretend he is Tarzan.
Sylvia watches her mom put a napkin on her lap during restaurant dining, so she does the same.