How do primary waves differ from secondary waves?

Primary waves, also known as compressional waves or P-waves, are unique in that they can travel through solids, liquids, and gases. This ability to move through a variety of materials is a defining characteristic of primary waves. They are the first type of seismic wave generated by an earthquake, and their speed and capability to travel through different states of matter is crucial for understanding how seismic activity propagates through the Earth.

In contrast, secondary waves, or S-waves, are shear waves that can only travel through solids and do not move through liquids or gases. This distinction is essential when interpreting seismic data, as it helps scientists determine the composition and state of Earth's interior based on the types of waves that are detected after an earthquake.

The correct choice reflects the fundamental nature of primary waves as versatile seismic waves, capable of traversing different mediums, which is essential knowledge in the field of seismic physics.