What characteristic of longitudinal waves contributes to their increased velocity compared to shear waves?

The correct choice highlights that the compression of the medium is key to the increased velocity of longitudinal waves compared to shear waves. Longitudinal waves, such as those found in sound, move by compressing and rarefying the medium through which they travel. This method of energy transfer involves particles in the medium moving back and forth in the same direction as the wave, allowing the wave to propagate efficiently.

In contrast, shear waves, which move through a medium by displacing particles perpendicular to the direction of wave propagation, require a more rigid medium to travel through. The shear strength of the material itself plays a critical role in the speed of shear waves. Because shear waves cannot travel through fluids and are slower in solids compared to longitudinal waves, the intrinsic capacity for compression in longitudinal waves allows them to travel faster through most materials.

Other options, such as particle motion, transverse motion, and wave reflection, do not specifically address the fundamental interaction with the medium that impacts the speed of wave propagation as efficiently as the compression does. While these factors are relevant to wave behavior and characteristics, they do not directly explain why longitudinal waves have a higher velocity in comparison to shear waves.