Question

how do scientists primarily study and gain knowledge about the earths interior structure? by studying seismic waves from earthquakes by drilling deep boreholes by studying rock samples from volcanoes

Explanation:

Scientists mainly study seismic waves from earthquakes. Seismic waves change speed and direction when passing through different materials in the Earth's interior. By analyzing these waves, scientists can infer the structure of the Earth's interior. Drilling deep boreholes is limited by depth (current deepest boreholes are only a few tens of kilometers, while the Earth's radius is about 6371 km). Studying rock samples from volcanoes only gives information about the upper mantle and crust near volcanic areas, not the entire interior structure.

Answer:

by studying seismic waves from earthquakes