The correct response is:
Both waves cause earthquakes.
P-waves (primary waves) and S-waves (secondary waves) are types of seismic waves generated by earthquakes. P-waves are compressional waves that move the ground in the direction they travel, while S-waves are shear waves that move the ground perpendicular to their direction of travel. However, since the question asks for a description that applies to both types of waves, the statement "Both waves cause earthquakes" is the accurate answer.