What Led to the Ecological Disaster of the 1930s in the Great

What led to the ecological disaster of the 1930s in the Great Plains region?

A) a flood that eroded away all the topsoil in the region
B) a lack of available farm labor caused by the growth of employment on the east coast during that decade
C) a drought, combined with dust storms that blew away the topsoil
D) Mormon belief systems, which advocate the clear-cutting of all land