Answer:
Compressions
Explanation:
A longitudinal wave is a wave in which the direction of propagation of the wave and the direction of the displacement of the particles of the wave are parallel.
As the wave propagates, the particles do not move, but, oscillate back and forth about their equilibrium position, and there are thus regions of high pressure called compressions and regions of low pressure called rarefactions.
The amplitude is thus the distance between successive compressions.
