Answer:
D. a system in which people are enslaved permanently on account of their race
Step-by-step explanation:
A system in which people are enslaved permanently on account of their race does not describe a form of slavery traditionally practiced in Africa because racial slavery was introduced by the Europeans during the trans-Atlantic slave trade. Before that, slavery in Africa was based on other factors, such as kinship, debt, war, or social status. Enslaved people in Africa were not necessarily considered inferior or different from their enslavers, and they had some rights and opportunities for social mobility. Racial slavery, on the other hand, was based on the idea that some races were inherently superior or inferior to others, and that enslaved people were property with no rights or dignity. Racial slavery was also permanent and hereditary, meaning that enslaved people and their descendants could never be free or equal.