The line that has been the representation of the region of rarefaction in the diagram has been the line below the top line.
The diagram has been the representation of the movement of the particles under the influence of wave energy. The particles have been moving from left to right in the longitudinal order with a gain of energy.
The rarefaction has been the instance where the density of the waves has been lesser or where there has been one wavelength of the wave.
The diagram has been representing, at the line below the top arrow, there have been lesser density of the wave particles, thus, the region of rarefaction has been the instance in the lines below the top line.
For more information about the rarefaction, refer to the link:
https://brainly.com/question/1326823
