Except for the statement A, all other statements can be argued to be negative outcomes of the invention of the cotton gin. But in the need to choose only two, the most negative are C and D.
Despite the cotton gin making processing faster, it produced more demand for labor instead of less. The cotton production's radical growth was based primarily on slave labor. Thus:
Statements B and E are negative since the prominence of the United States in the world cotton production, due to a tremendous increase in production, was reached based on a more violent exploration of slave labor.
Statements C and D refer more directly to negative outcomes of the cotton gin. They explain how numbers in statements B and E were achieved. Slave labor was a repudiation of black people's status as humans. It was obtained through continuous violence and torture, and it increased due to the invention of the cotton gin.