Answer:
D. Nathan applies enough force through pushes to move the piano
Step-by-step explanation:
What moves the piano is a net force that is applied through the effort of Nathan on the instrument.
Force is a pull or push on a body.
When force is applied on a body, it causes the state of motion of the body to change.
Therefore, if a body has a net force greater than zero, the body will in likewise begin to move. As Nathan pushes on the piano, it will eventually move.