Which of the Following Is True of the Eastern African

Which of the following is true of the Eastern African states referred to as "secondary empires"?

A) They were not directly controlled by Europeans but were supplied with European weapons.
B) Their primary slave trade was with the Islamic regions of North Africa and the Middle East.
C) Slavery was prominent within East African states.
D) Some slaves were traded to the Indian Ocean regions controlled by European countries.
E) all of the above