By the Early 1700s, Slavery Had Become Concentrated in the Southern

By the early 1700s, slavery had become concentrated in the southern colonies.  Economic factors that explain this demographic trend include all of the following except

A) the South's use of the primogeniture system.
B) economies of scale available in the production of the South's primary crops.
C) a climate that allowed for year-round agricultural production.
D) early laws that prohibited slavery in most of the New England and Middle colonies.