Correct Option: C

Chernozem or black earth variety of soil is rich in organic matter in the form of humus. It is generally a modified type of loess. True chernozem is black in color, but there are various grades, shading off into gray and chestnut-brown soils. It forms in areas that have cold winters, hot summers, and rapid evaporation of precipitation; generally only tall grass is found native on chernozem.