What component is used as a filter for the passage or rejection of specific frequencies?

The correct choice is tuned circuits, which are specifically designed to allow certain frequencies to pass through while rejecting others. Tuned circuits, often consisting of inductors and capacitors in resonance, are used in a variety of applications including radio transmitters and receivers, where it is essential to select a particular frequency for signal processing.

When a tuned circuit is in resonance, it presents a low impedance at its resonant frequency, allowing signals at that frequency to pass through efficiently. Conversely, it presents a high impedance to other frequencies, thereby filtering them out. This frequency-selective property is crucial in communications, audio equipment, and many other electronic systems, making tuned circuits integral components in the design and function of devices that require frequency discrimination.

The other options, while important in electronic circuits, do not function primarily as filters for specific frequencies in the same manner. Transformers are used for voltage transformation and isolation, inductors typically oppose changes in current rather than filtering specific frequencies, and capacitors store and release electrical energy but do not themselves function as frequency-selective components without being part of a tuned circuit.