Which of the following are the two main types of single-phase motors?

The two main types of single-phase motors are split-phase motors and capacitor-start motors. These motors are widely used for their ease of construction and operation in various applications, such as in household appliances and small machinery.

Split-phase motors operate by providing a phase shift between the starting and running windings, which is crucial for generating the necessary starting torque. This is achieved through the use of two windings that are placed at a specific angle to each other in the motor.

Capacitor-start motors, on the other hand, utilize a capacitor in series with the starting winding to enhance starting torque. The capacitor creates a leading phase current that provides a better starting condition and improved efficiency when compared to split-phase designs.

Other options like capacitor-start motors paired with synchronous motors or induction motors alongside universal motors do not accurately represent the predominance or purpose of these specific types in the realm of single-phase applications. Each of the other combinations includes at least one type of motor that either does not function as a single-phase motor (like synchronous and DC motors) or represents a different category of motors.