Question

what is the rarefaction of a longitudinal wave?
the place where the particles are closest together
the resting position of the wave
how fast the parts of the wave move
the place where the particles are farthest apart

Explanation:

In a longitudinal wave, particles move parallel to the wave's direction. Compressions are where particles are closest; rarefactions are where they're farthest apart. The resting position isn't related to rarefaction. How fast parts move refers to wave speed, not rarefaction.

Answer:

the place where the particles are farthest apart