Explanation: A modulation-acceptance bandwidth test is performed to determine the range of frequencies a receiver can effectively process a modulated signal without significant distortion or loss of information. This directly measures the receiver's *effective bandwidth* – how wide its RF and IF filters are, allowing it to "accept" the full spectrum of the desired modulated signal. * **A) Ascertain the audio frequency response of the receiver:** This relates to how well the audio output stage reproduces different audio frequencies, which is a separate characteristic from the RF/IF bandwidth. * **B) Determine whether the CTCSS in the receiver is operating correctly:** CTCSS (Continuous Tone-Coded Squelch System) operation is tested by verifying its tone detection and squelch control, unrelated to the receiver's overall RF/IF bandwidth. * **C) Verify the results from a 12 dB SINAD test:** SINAD (Signal-to-Noise And Distortion) measures receiver sensitivity and audio quality. While bandwidth affects SINAD, a modulation-acceptance bandwidth test is a different measurement, not a verification of SINAD results.