Final answer:
Earthquakes cause the seismic waves that help scientists understand the composition of Earth's interior. These waves are detected and analyzed to infer the structure and composition of Earth's different layers.
Step-by-step explanation:
The waves that have provided scientists with most of their understanding about the Earth's interior are primarily caused by earthquakes. When an earthquake occurs, it generates seismic waves that travel through the Earth's interior. These waves can be detected and measured by seismographs. By analyzing the speed, direction, and behavior of these waves, scientists can infer the structure and composition of different layers of the Earth's interior. Therefore, the correct answer to your question is A. Earthquakes.
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