In the early 1700's South Carolina raised the import duties on slaves coming from the West Indies, which most likely resulted in C; More slaves being imported directly from Africa. This is so because it was relatively cheaper to import directly from Africa opposed to the West Indies.
Take off D; the North had won some battles up to that point. Rip off A; the South would never let go of slavery. Take off B, since the Union had some wins already. You can now clearly see where the answer is.
