Answer the following question given this paragraph: 

Earth’s crust contains a lot of oxygen. The oxygen can combine with other elements to create oxide minerals. Oxides contain one or two metal elements combined with oxygen. Oxides are different from silicates, because they do not contain silicon. Many important metals are found as oxides. For example, hematite and magnetite are both oxides that contain iron. Hematite (Fe 2 O 3 ) has a ratio of two iron atoms to three oxygen atoms. Magnetite (Fe 3 O 4 ) has a ratio of three iron atoms to four oxygen atoms. Notice that the word “magnetite” contains the word “magnet. " Magnetite ( Figure below ) is a magnetic mineral.


Q: What layer of earth contains abundant oxygen, which can combine with other elements to create oxide minerals?

 Choices:

- the core

- the surface

- the tectonic plates

- the crust

A:
the crust
