Explanation: A self-rectified circuit refers to a simple detector that directly converts a modulated radio frequency (RF) signal into an audio signal without requiring a separate local oscillator or dedicated power for the rectification process itself. It effectively extracts the modulation envelope. A-2 emissions are tone-modulated continuous wave (MCW). This means an RF carrier is amplitude-modulated by a constant audio tone. A self-rectified circuit, often a simple diode detector, can detect the amplitude variations of this A-2 signal. The circuit "rectifies" the incoming RF carrier, recovering the original audio tone for direct audible reception. Options A and D describe different emission types or circuit functions unrelated to this specific detection method. Option B describes an op-amp feedback loop, which is a general electronics concept, not the definition of a self-rectified circuit in the context of radio signal detection.