Which seismic wave causes particles of rock to move back and forth?

The choice of P Waves as the correct answer is accurate because these waves are characterized by their ability to compress and elongate the material they travel through. When P Waves, also known as primary waves or compressional waves, propagate through the Earth, they create a series of compressions and rarefactions in the rock. This motion causes particles of rock to move in the same direction as the wave itself—essentially back and forth along the path of the wave.

P Waves are the fastest seismic waves and can travel through solids, liquids, and gases. This property allows them to be the first waves detected by seismographs during an earthquake. Their nature of moving particles in a back-and-forth motion, aligned with the direction of wave propagation, distinguishes them from other types of seismic waves.

In contrast, S Waves (secondary waves) move particles perpendicular to their direction of travel, while surface waves cause more complex motions and are generally responsible for most of the damage during an earthquake. Body waves encompass both P Waves and S Waves, but the specific behavior of P Waves is what makes them unique in this context.