The purpose of commutator in a generator is toa.Reducing arc at the brushesb.  Convert DC to ACc.Reduce frictiond.Convert AC to DC

The purpose of a commutator in a generator is to convert AC to DC. Here's a step-by-step explanation:

1. A generator produces alternating current (AC). This is because the direction of current changes every half cycle as the coil rotates in the magnetic field.

2. However, many devices require direct current (DC), which flows in one constant direction.

3. This is where the commutator comes in. It's a device attached to the ends of the generator coil.

4. As the coil rotates, the commutator reverses the connections with the external circuit every half cycle.

5. This means that every time the current in the coil changes direction, the commutator changes the direction of the current in the external circuit.

6. As a result, the external circuit always receives current flowing in the same direction - direct current (DC).

So, the correct answer is d. Convert AC to DC.