Explanation: Single Sideband (SSB) signals transmit only one sideband and suppress the carrier frequency to conserve power and bandwidth. A standard AM detector, which relies on the presence of the carrier for demodulation, cannot directly recover the audio from an SSB signal. The Beat Frequency Oscillator (BFO) provides a locally generated carrier frequency that is precisely tuned and re-injected into the receiver's detector stage. This artificially re-inserted carrier mixes with the incoming SSB signal, allowing the detector to properly demodulate the signal and reproduce the original audio information. Without the BFO, SSB signals would sound like distorted, unintelligible "monkey chatter." Option B is incorrect because the BFO only re-inserts the carrier, not a missing sideband. Option C refers to removing a carrier, which is the opposite of the BFO's function and applies to different transmission types. Option D describes a function unrelated to the BFO's role in SSB demodulation.