How does the pulley make work easier?

a
It changes the mass of the piano, making it easy to raise
b
It changes the amount of energy needed to raise the piano
c
It changes the direction of the force applied to raise the piano
d
It changes the duration of time to raise the piano

c. It changes the direction of the force applied to raise the piano. By using a pulley, the force required to lift an object can be spread out over multiple ropes or cables, and the direction of the force can be changed to make lifting easier.