Final answer:
The fastest seismic waves are compressional waves, also known as P waves. They can move through any type of medium (solids, liquids, or gases) and cause the medium to compress and expand.
Step-by-step explanation:
The fastest seismic waves are C) compressional waves, also known as P waves (primary waves). These waves can move through all types of mediums - solids, liquids, and gases. They cause particles in the medium to move in a direction parallel to the wave direction, hence compressing and expanding the medium. The speed of P waves varies depending on the medium but they are always the first waves to be detected by a seismograph due to their high velocities.
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