What is the chernozem and where is it found ?

Chernozems (from the Russian words for “black earth”) are humus-rich grassland soils used extensively for growing cereals or for raising livestock. They are found in the middle latitudes of both hemispheres, in zones commonly termed prairie in North America, pampa in Argentina, and steppe in Asia or in eastern Europe.

I’m confused ///: : : :

The correct answer is a)  a resource with a limited supply; it will run out.