Jake and Darnell are creating flashcards to help them study for a test on Earth's internal structures. Which statement below is the only factual statement that they should include on their flashcards?
A. Earth's liquid inner core creates a magnetic field.
B. Earth's core can be studied directly by drilling into the crust.
C. Scientists use seismic wave data to study the Earth's structure.
D. Materials that make up Earth's layers all have the same densities.
