Explanation: When a VHF radio receiver fails to produce any audible output from the speaker and the squelch control has no effect, it indicates a problem in the audio amplification stage or a system-level mute. * **AF amplifier defective:** The Audio Frequency (AF) amplifier is the final stage that boosts the demodulated audio signal to drive the speaker. If this amplifier fails, no sound will reach the speaker, regardless of whether a signal is being received or if the squelch is open. The squelch circuit might be working internally, but because the path to the speaker is broken, the squelch control appears to have "no effect" on the audible output. * **Transmitter Push-To-Talk (PTT) circuit activated:** Many transceivers automatically mute the receiver audio when the PTT circuit is activated (to prevent feedback or allow side-tone monitoring). If the PTT circuit is stuck in the "transmit" position, even if the transmitter isn't active, the receiver's audio path would remain muted, resulting in no sound from the speaker and the squelch control having no audible effect. Options A, B, and D describe failures in earlier stages of the receiver (RF amplifier, Local Oscillator, Mixer). If these stages failed, the receiver would likely produce static noise if the squelch were open, and the squelch control *would* typically still function to silence that noise or fail to open if it were set to open only on a signal. The specific symptom of "no audible output" AND "squelch control has no effect" points to a fault in the final audio output path or a complete system mute.