Question

what is the wavelength of a longitudinal wave?
the distance from compression to compression or rarefaction to rarefaction
how compressed or rarefied the medium becomes
the speed of the wave
the distance from crest to trough or trough to crest

Explanation:

Wavelength is defined as the distance between two consecutive identical points on a wave. For longitudinal waves, these identical points are consecutive compressions or consecutive rarefactions. The other options describe wave amplitude, wave speed, and a measurement for transverse waves, respectively.

Answer:

the distance from compression to compression or rarefaction to rarefaction