Which part of a DC motor is responsible for creating the mechanical revolutions of the unit? 

The part of a DC motor responsible for creating the mechanical revolutions of the unit is the rotor.

Rotor: The rotor is the rotating part of a DC motor. It consists of a coil (or coils) wound around an armature core. When electric current flows through the coil, it interacts with the magnetic field produced by the stator (stationary part of the motor), generating a torque that causes the rotor to rotate. This rotation results in the mechanical output of the DC motor.
The other components mentioned are also important in the operation of a DC motor:

Brushes: Brushes are conductive components that maintain electrical contact with the rotating commutator. They allow the flow of current from the power source to the armature windings.

Commutator: The commutator is a rotary switch that reverses the direction of current in the armature windings, ensuring that the torque produced by the interaction with the magnetic field remains unidirectional, leading to continuous rotation of the rotor.

Stator: The stator is the stationary part of the DC motor that produces a magnetic field. It interacts with the rotor's magnetic field, inducing the motion of the rotor.

In summary, while the stator, brushes, and commutator play crucial roles in the functioning of a DC motor, the creation of mechanical revolutions is primarily attributed to the rotor's rotation induced by the interaction with the stator's magnetic field. Therefore, the correct answer is: (1) Rotor