The diagram shows an electric motor. An illustration of a coil of wire connected to a battery labeled Z. The coil is in between a north pole and a south pole. The coil is rotating clockwise. The point where the positive electrode of the battery is connected to it is labeled Y. The long straight with that it rotates around is labeled W. The ring with a slit that the battery is connected to is labeled X.
Which part of the motor is responsible for reversing the flow of current?

W
X
Y
Z