Which types of signals are applied to transistors?

Transistors require specific types of signals to function effectively, and the correct choice focuses on two crucial aspects: input signals and bias signals.

Input signals are the actual signals that you want to control or amplify through the transistor. These can be varying in nature, depending on the application—for instance, they can be audio signals in an amplifier or a control signal in a switch.

Bias signals are essential because they set the operating point of the transistor. Without proper biasing, a transistor might operate in an undesirable region, leading to distortion or inefficient performance. The biasing ensures that the transistor remains in the active region, providing reliable amplification or switching.

This interplay of input and bias signals is fundamental to the operation of transistors in both analog and digital circuits, but the terminology in the correct answer highlights the necessary aspects for proper transistor functionality. Other options focus on different components or types of signals that may not directly contribute to the fundamental operation of transistors as input and bias signals do.