Work must be done by (kinetic or potential energy)

I believe it is kinetic

Explanation:

Kinetic energy is in physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes.

So if something is doing work it has kinetic energy