Those Who Claim That the Effects on Africa from the Slave

 Those who claim that the effects on Africa from the slave trade have been exaggerated point to which of the following? 

A) many African societies had no contact with the slave trade.
B) farming and herding remained the principle economic activity of Africa through the years.
C) many African societies had slave markets of long standing
D) all of the answers are correct.
E) new plants that were introduced into Africa produced more calories per acre than traditional crops.