C3) our knowledge of the earth's interior has been gained mainly by: a) drilling deep exploration wells b) excavating deep mine shafts c) studying the behavior of seismic waves d) observing volcanic eruptions iwa

c) studying the behavior of seismic waves

Explanation:

The Earth's interior is formed by several layers: the crust, mantle, and core. The crust is accessible and scientists can experiment directly on it to determine its composition, for more distant layers scientists, rely on the analysis of seismic waves and gravity, as well as magnetic studies.

Since it is impossible to drill to the center of the Earth, scientists use seismic waves and how they travel during and after an earthquake as a tool to understand the earth's interior composition, they measure the time it takes for waves to get to the seismometer and their direction.

Considering this information we can conclude that the correct answer is c) studying the behavior of seismic waves.

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c. seafloor spreading occurs.

d. crust becomes molten rock.

e. denser plates slide under lighter plates.