The amplitude of the wave is relative to the maximum displacement of the particle of the medium from its position of rest. In this sense, the amplitude is the distance from the rest position to the crest, or from the same position to the th trough position, or as the height of the wave. Also, the energy that the wave carries is related to the amplitude of the waves. High energy waves are characterized by high amplitude, while the low energy wave is characterized by low amplitude.
The answer is: D.