Explanation: An SSB two-tone test evaluates a transmitter's linearity and susceptibility to generating intermodulation distortion, which manifests as unwanted sideband splatter. The test uses **two non-harmonically related audio signals** (pure sine waves) because if the input tones were harmonically related, the intermodulation products created by the transmitter's non-linearity would overlap with the harmonics of the input tones, making them indistinguishable. Non-harmonic tones ensure that any generated intermodulation products (sums and differences of multiples of the input frequencies) are distinct and easily observable on a spectrum analyzer. These signals must be **within the modulation band pass of the transmitter** (e.g., 300-3000 Hz for voice) to simulate typical operating conditions and test the transmitter's performance within its intended frequency range. * A) Two signals of the same frequency, regardless of phase, would act as a single tone, not producing intermodulation products. * C) Square waves contain multiple harmonics, complicating the analysis of the transmitter's non-linearity. Pure sine waves are preferred for a precise test. * D) Harmonically related tones would cause intermodulation products to coincide with input harmonics, preventing accurate assessment of non-linear distortion.