Which of the Following Is Not a Reason Why Africans

Which of the following is not a reason why Africans enslaved other Africans, and sold them to Europeans?

A) Africans at the time did not have a sense of themselves as "Africans," and had not really developed a concept of racial solidarity.
B) Warfare and interethnic rivalries among African tribes contributed; selling members of defeated tribes proved a way to get rid of opponents.
C) African tribes were forced under threat of annihilation or war to sell others to the Europeans.
D) African tribes actually did not enslave other African tribes.