Answer:
a person climbs a set of stairs
Step-by-step explanation:
A person climbing a set of stairs increases his height, which also increases his gravitopotential energy. Gravitopotential energy increases with height as you move further away from the surface of the Earth.
A wind up toy winding down is already expending its stored up potential energy. An apple falling from a tree is already losing its gravitipotential energy. A firecracker that explodes is already using up the potential energy stored in its chemical. All these are cases where the potential energy is decreasing.