The correct answer is C. stops S-waves.
When an earthquake occurs, it generates seismic waves that travel through the Earth. These waves include P-waves (primary waves) and S-waves (secondary waves). P-waves are compressional waves that can travel through both solid and liquid mediums, while S-waves are shear waves that only propagate through solid materials.
The outer core of the Earth is composed of liquid iron and nickel, which means it does not allow S-waves to pass through. This phenomenon is known as the S-wave shadow zone. When seismic waves encounter the outer core, the S-waves are unable to penetrate it, causing a gap in the wave pattern on the opposite side of the Earth from the earthquake's epicenter.
This shadow zone is crucial in determining the physical state of the Earth's inner core because it indicates the presence of a liquid outer core. By studying the distribution of seismic waves during an earthquake, scientists can gather valuable information about the Earth's internal structure.
It is worth noting that although the outer core stops S-waves, it does not stop P-waves. P-waves can still pass through both the outer and inner core, but they undergo refraction and change in speed as they travel through different materials. This refraction provides insights into the composition and physical properties of the Earth's layers.