Final answer:
Diodes are the components commonly used as rectifiers in electrical circuits. Anodes and cathodes do not act as rectifiers but are the terminals of a diode.
Step-by-step explanation:
In electrical circuits, diodes are commonly used as rectifiers. A rectifier is a device that converts alternating current (AC) to direct current (DC), and diodes play a crucial role in this process. Diodes are semiconductor devices that allow current to flow in one direction only, which is essential for the rectification process. The function of anodes and cathodes are related more to the operation of components like batteries and electrolytic cells where they serve as the positive and negative terminals, respectively. In the context of rectification, however, the terms anode and cathode refer to the positive and negative sides of a diode but do not themselves act as rectifiers. Therefore, the correct answer to the question is C. 3, indicating that diodes are the components used for rectification in electrical circuits.