Final answer:
The distance from one compression to the next in a longitudinal wave is its wavelength, which is the length of one complete cycle of the wave.
Step-by-step explanation:
The distance from one compression to the next in a longitudinal wave is C) Its wavelength. In a longitudinal wave, areas of higher pressure, termed compressions, and areas of lower pressure, known as rarefactions, are evident. The wavelength of a longitudinal wave is measured as the distance between two consecutive compressions or two consecutive rarefactions. It represents the length of one complete cycle of the wave. This is not to be confused with amplitude, which is the maximum displacement of a point on the wave from its rest position, or with frequency, which is the number of waves that pass a point in a certain period of time.