Explanation: Block 50 in a typical FM receiver block diagram (such as Fig. 8A1 from the FCC question pool) is located after the IF amplifier stages and before the audio amplifier. This position is characteristic of the demodulator circuit. A **discriminator** is a type of FM detector that converts the frequency variations of the incoming FM signal into corresponding amplitude variations. These amplitude variations are then further processed to extract the original audio information. * **A) IF amplifier** is incorrect because IF amplifiers precede the discriminator, amplifying the signal at an intermediate frequency. * **B) AFC amplifier** (Automatic Frequency Control) is part of a feedback loop to stabilize the local oscillator frequency, not the primary demodulation component. * **D) Crystal detector** is primarily used for demodulating AM (Amplitude Modulation) signals, not FM (Frequency Modulation).