Which Statement Concerning the West African Empires Prior to 1600

Which statement concerning the West African empires prior to 1600 is true?

A) They engaged in vigorous trade, were Islamic, and were known for their wealth.
B) They had no written language and no transportation infrastructure.
C) They were infested with tsetse flies and therefore unable to develop a state bureaucracy.
D) They were generally warrior states with little inclination to develop agriculture.
E) They were ruled over by kings whose absolute political power was based on ruthless use of force.