What distinguished this black belt region of cotton production from ot

What distinguished this black belt region of cotton production from other cotton production areas such as South Carolina?

A) This new land in the black belt was unusually susceptible to extended periods of drought.
B) Frequent crop rotation was required every couple of years to keep the black belt land fertile for cotton production.
C) The planters in the highly fertile black belt could produce three times more pounds of cotton per acre than cotton planters could in coastal South Carolina.
D) Slave labor was of decreasing importance to successful cotton production in this region in comparison to other cotton producing regions such as coastal South Carolina.

ANSWER
Answer: C