Which term describes the outermost rigid shell of the Earth, including the crust and upper mantle?

• A. Biosphere
• B. Atmosphere
• C. Lithosphere
• D. Hydrosphere

Answer: (C)

The term describes the outermost rigid shell of the Earth, covering both the crust and the rigid part of the upper mantle. This shell is known as the lithosphere. It is the solid, brittle layer that forms the tectonic plates, sitting atop the weaker, partially molten asthenosphere that allows those plates to move.

This distinction matters because the atmosphere is the gaseous envelope surrounding Earth, the hydrosphere includes all water bodies, and the biosphere encompasses living organisms and their environments. None of those late layers describe the rigid shell that includes the crust and upper mantle.