The Dust Bowl Experience of the United States in the 1930s

The Dust Bowl experience of the United States in the 1930s was caused primarily by

A) planting grains in soils that could only support leaf crops sustainably.
B) lack of any soil conservation practices,continuous cropping,coupled with natural drought.
C) lack of enforcement of the soil conservation provisions of the 1862 Homestead Act.
D) attempts to farm areas with desertlike climate and thin topsoil.