What type of distortion causes amplitude modulation of one signal to affect another signal?

The phenomenon where the amplitude modulation of one signal inadvertently affects another signal is termed cross-modulation. Cross-modulation typically occurs in systems where multiple signals share the same channel or bandwidth, leading to interference that can alter the amplitude of one signal based on the modulation characteristics of another. This can create various issues in transmission systems, such as decreased clarity or distortive effects in the reception of those signals.

In contrast, linear distortion generally refers to alterations in amplitude or phase that occur uniformly across frequencies, thereby not causing one signal's modulation to impact another's. Predistortion involves preemptively adjusting a signal to counteract expected nonlinearities in a system but does not directly relate to one signal affecting another through modulation. Non-linear distortion occurs when a signal's characteristics are altered in a non-linear fashion, typically affecting the same signal rather than interacting with other independent signals.

Thus, cross-modulation is distinctly characterized by the interaction of multiple signals, making it the correct answer in this context.