Which layer is described as hot and solid material between the Earth's crust and core?

The mantle is the layer of the Earth located between the crust and the outer core, and it is characterized by being hot and composed of solid material. This layer extends to a depth of about 2,900 kilometers below the surface and is primarily made up of silicate rocks that can flow over geological timeframes, which is critical for processes such as plate tectonics and volcanic activity.

The mantle consists of the upper and lower mantle, and while the upper mantle interacts with the crust and is partially molten in the asthenosphere region (allowing for tectonic movement), the overall composition of the mantle remains solid. The high temperatures and pressure conditions result in a solid state, but the rock can behave like a viscous fluid over long periods.

In contrast, the outer core is a molten layer primarily composed of iron and nickel, while the lower crust refers specifically to the solid rock layer bordering the mantle. The upper mantle, while part of the mantle, does not encompass the entirety of the characteristics described in the question, particularly the solid nature of the entire layer. Thus, the mantle as a whole is the correct choice for describing the hot and solid material lying between the Earth's crust and core.