The correct answer is D) Africans always let their slaves go free after two years of service.
What is not a true statement about slavery in Africa is "Africans always let their slaves go free after two years of service."
What was true about slavery in Africa was that Africans did not sell the children of slaves, slavery existed long before European contact, and slaves were not pushed to work the land so hard. The dominant Emperor of some territory used slaves for his service. They were used as domestic servants, workers or in the fields. It was not the kind of slavery imposed by the Europeans where they demanded hard work and long hours to slaves. But definitely, slavery was in place in Africa long before the white European arrived.