Height of transverse wave or density of the compression of a longitudinal wave

compression

Explanation:

A longitudinal wave is defined as a wave in which the oscillations of the particles occur in a direction parallel to the direction of propagation of the wave. An example of longitudinal wave is sound waves, in which particles of air (or any other medium) are displaced back and forth along the direction of propagation of the wave.

The oscillations of these particles produce regions which have lower density of air particles and regions which have higher density of air particles. The former are called rarefactions, while the latter are called compression.

The problem is asking us for the name of the regions where the density is maximum: therefore, the correct answer is compression.