Which is an example of extrinsic motivation?

exercising because it feels good and you enjoy it
buying a new pair of shoes because your favorite sports player wears them
preparing for a party over at your house because you like having friends over
going to bed early because you're tired and want to feel rested

Extrinsic motivation is refers to every behaviour that's motivated by an external stimulus. When we do things like going to the gym or going to parties, always we do it with a certain motivation, which can be developed through to source: extrinsic and intrinsic.

Intrinsic motivation is when we do something because we enjoy it, we desire to do it, because it can gives us some pleasure. So, in other words, the reason about our acts is inside of us.

Extrinsic motivation is when we act because something or someone else gives us a reward, a reason to act, like money for example. So, the reason about our acts is external.

Therefore, the correct answer is the second one, because it says that we buy shoes because someone else wears them, this means that the reason of action is outside, it's external.