What is Earth's solid outer layer, which includes rocks, called?

The solid outer layer of the Earth, which comprises the crust and the uppermost portion of the mantle, is known as the lithosphere. This layer is characterized by its rigidity and includes various types of rocks and minerals that form the Earth's surface. The lithosphere is crucial for supporting terrestrial life, providing the foundation for ecosystems and various geological processes.

Understanding the other options further clarifies why lithosphere is the correct choice. The hydrosphere refers to all the water bodies on Earth, including oceans, rivers, lakes, and water vapor in the atmosphere. The atmosphere encompasses the layer of gases surrounding the Earth, essential for weather and climate. The biosphere includes all living organisms and the ecological interactions in environments on Earth. Each of these spheres plays a vital role in Earth's system, but only the lithosphere specifically pertains to the solid outer layer and the rocks that comprise it.