Which of the following statements is true about the Earth's crust?

The statement that the Earth's crust is mostly solid rock is accurate because the crust is the outermost layer of the Earth, characterized by a solid state. It is composed largely of igneous, metamorphic, and sedimentary rocks. The crust varies in thickness, being thinner under the oceans (oceanic crust) and thicker under continents (continental crust), but fundamentally, it remains solid and contributes to the Earth's geological makeup and processes.

In contrast, the crust is not the hottest layer of the Earth; that distinction belongs to the inner core, which is extremely hot due to high pressure and radioactivity. Additionally, the crust is not molten, as a molten layer is referred to as the mantle beneath the crust, which contains semi-solid rock that can flow slowly. The crust is also not positioned between the outer and inner core; those layers are significantly deeper within the Earth, with the crust being the top layer directly above the mantle.