Amplitude modulation can best be described as...

Amplitude modulation is best described as the periodic change in the amplitude of a signal. In amplitude modulation, the strength or amplitude of a carrier wave is varied in proportion to the waveform being sent, which typically contains information, such as audio signals in radio broadcasting. This means that the amplitude of the signal carries the information, creating a modulated signal.

Modulation, in general, involves transforming a base signal to encode information for transmission, and amplitude modulation specifically focuses on altering the amplitude. Understanding this concept is crucial in fields such as telecommunications and audio signal processing, where it plays a significant role in how data is transmitted over distances and how sound is produced and received.

Other options may touch upon different aspects of signal processing, but they do not accurately capture the definition or scope of amplitude modulation.