Which method is used to obtain direct data about Earth's interior by collecting rock samples?

• A. Seismic waves are studied to see how they travel through Earth.
• B. Measuring magnetic field
• C. Drilling into the Earth to obtain rock samples
• D. Observing surface distribution

Answer: (C)

Direct sampling of the interior comes from actually drilling into the Earth to bring up rock from depth. This gives you real, physical material that can be analyzed in the lab for mineralogy, chemistry, age, and other properties, providing direct evidence about what lies beneath the surface. Other approaches—studying how seismic waves travel, measuring the magnetic field, or mapping surface rocks—tell us about the interior only by inference or indirect signals; they rely on models to interpret what the data imply about deep structure. Drilling is the only method that yields firsthand samples from depth, even though the deepest boreholes reach only a small fraction of the Earth's radius.