Final answer:
The crust is a part of the lithosphere, which also includes the uppermost mantle. The lithosphere behaves as a rigid, brittle layer, distinguishing itself from the underlying, plastic asthenosphere, both essential in tectonic plate interactions.
Step-by-step explanation:
The correct relationship between the crust and the lithosphere rests on understanding that Earth's outer surface consists of the crust, which is a cold, thin, brittle shell made of rock that exists in two distinct types, each with unique properties. The lithosphere, which is approximately 100 kilometers thick, is the outermost mechanical layer of the Earth, behaving as a rigid, brittle solid and comprising both the crust and the uppermost portion of the mantle. While the crust is part of the lithosphere, it is not synonymous with the lithosphere as it is distinguished by both its chemical composition and mechanical properties.
The lithosphere divides from the underlying asthenosphere, which is characterized by its plasticity and ability to flow, as it's composed of partially molten mantle material. This division has significant implications for tectonic plate interactions, such as pulling apart, subduction, sliding alongside, and compression, which are instrumental in shaping the geology of our planet.