Final answer:
The RF amplifier is the stage in a receiver that has both its input and output circuits tuned to the desired received frequency, enhancing signal strength with selectivity.
Step-by-step explanation:
The stage of a receiver that has its input and output circuits tuned to the received frequency is the RF (Radio Frequency) amplifier. The RF amplifier is designed to boost the strength of the incoming radio frequency signal while maintaining the quality of the signal.
Its tuning capability allows it to select the desired frequency (or frequencies) among all the signals that reach the antenna. This selective process helps to ensure that the receiver can focus on and amplify the intended signal while filtering out others.