Describe the structure of the study independent variables , dependent variables and detail why the researchers would have used random allocation.

because of

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added