Which of the following best describes unstable equilibrium?

In unstable equilibrium, a small push moves the body away from its position, and it does not come back. Its centre of gravity falls as it moves.

A ball balanced at the top of a hill is like this. A slight nudge makes it roll down, and it never returns to the top.

A ball resting at the bottom of a bowl is in stable equilibrium. If you push it, it rolls back to the bottom.