Final answer:
The lithosphere contains both the continental and oceanic crusts along with the uppermost part of the mantle, forming a rigid, brittle layer just above the more plastic asthenosphere.
Step-by-step explanation:
The lithosphere is the outermost layer of Earth and contains both the continental crust and the oceanic crust as well as the uppermost part of the mantle. The continental crust consists of various igneous, metamorphic, and sedimentary rocks, generally being less dense and thicker than oceanic crust. In contrast, the oceanic crust is primarily made of denser volcanic rocks such as basalt. The uppermost mantle, together with the crust, behaves as a brittle, rigid solid, making up the lithosphere. Below the lithosphere is the asthenosphere, which is partially molten and behaves plastically, allowing it to flow. Therefore, the best description of what the lithosphere contains is both types of crust and the uppermost mantle.