Answer and Explanation:
The answer is D. The distance between two identical points on a wave.
A wavelength is used to describe the distance between two corresponding (identical) points on waves next to each other.
A. This is describing the amplitude of a wave, which is the distance from the crest (top) to the trough (bottom) of a wave.
B. This is talking about signals created from all noise sources, not specifically the wavelength
C. The number of waves in a certain amount of time is a frequency.
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