Answer: C. seismic waves & D. samples of rock
Explanation: Scientists record the seismic waves caused from the waveforms of different earthquakes to infer the structures below the crust of the Earth. They record these seismic waves through seismographs from a machine called the seismometer. Scientists also observe the samples of broken rock that they get from the destruction multiple different earthquakes to make comparisons and studies to provide us details of what the bottom of Earth’s crust looks like.