Final answer:
A device that combines a tuner, pre-amplifier, and power amplifier is known as a receiver, which is crucial for demodulating and amplifying signals in radio communications. The correct option is c).
Step-by-step explanation:
The combination of a tuner, pre-amplifier, and power amplifier into one unit is referred to as a receiver. This electronic device is essential in radio communications for picking up a signal and producing a usable output.
Specifically, in amplitude modulation, like with AM radio, a radio receiver is tuned to have the same resonant frequency as the carrier wave to pick up the signal.
The receiver's circuitry then decodes the variations in amplitude of the carrier wave to replicate the original audio signal, which is amplified to be heard through a speaker or recorded. Option c) is the correct one.