The correct answer is A. gearing.
Gearing is a mechanical system that uses gears to transmit power from one part of a machine to another. Gears are toothed wheels that mesh together and rotate at different speeds. The speed of a gear is determined by the number of teeth on the gear. A gear with more teeth will rotate slower than a gear with fewer teeth.
Gearing is often used to reduce the speed of a universal motor. This is because universal motors are typically very fast, and they can be difficult to control at high speeds. By using gearing, the speed of the motor can be reduced to a more manageable level.
Belts, brakes, and chains are also mechanical systems that can be used to transmit power. However, they are not as effective as gearing for reducing the speed of a universal motor. Belts are flexible bands that are used to connect two or more rotating shafts. Brakes are devices that are used to stop or slow the motion of a machine. Chains are metal links that are used to connect two or more rotating shafts.
Belts, brakes, and chains can be used to reduce the speed of a universal motor, but they are not as effective as gearing. Gearing is the most effective way to reduce the speed of a universal motor, and it is the method that is most commonly used.