What is the composition of the Earth's crust?

The Earth's crust is primarily composed of solid rock and minerals, making this the correct choice. The crust is the outermost layer of the Earth, varying in thickness, but typically it consists of a mix of igneous, sedimentary, and metamorphic rocks. It contains a variety of minerals that contribute to its structure and characteristics, such as quartz, feldspar, and mica.

This composition plays a crucial role in various Earth processes, including plate tectonics, erosion, and the rock cycle. The solid nature of the crust is essential for providing stability for life forms and the ecosystems that exist on the Earth's surface.

In contrast, the other options describe materials that are not representative of the Earth's crust. For example, liquid iron and nickel refer to the Earth's outer core, while semi-fluid magma pertains to the mantle layer beneath the crust. Composite organic materials do not adequately characterize the inanimate rocks and minerals that form the crust's structure. Thus, recognizing that the crust is made primarily of solid rock and minerals is key to understanding Earth's geological makeup.