This isn’t an answer but I could help you if you tell me the project requirements
And is it in slides from or essay?
There is really nothing to know. All you have to use is context clues and common sense. We know some synonyms for direct are manage and handle. Indirect means not direct, right? And we can't handle or manage earth's interior (core), right? Therefore, the study of earth's interior is an example of indirect observation because we cannot directly manage it.
Everything in Earth's<span> system can be placed into one of </span>four major<span> subsystems: land, water, living things, or air. These </span>four<span> subsystems are called "</span>spheres<span>." Specifically, they are the "lithosphere" (land), "hydrosphere" (water), "biosphere" (living things), and "atmosphere" (air).</span>
