What was Black Power?A) a movement calling for African Americans to rely on themselves to achieve change // B) a movement calling for the...

Of the options that you have given us, the best is A. 
Answers B and D are simply wrong.  Answer C is not really correct either even though the
Nation of Islam would have generally supported the idea of Black Power.  Although they
would have supported it, it was not they who came up with the
idea.

Black Power was an idea that was popularized by
Stokely Carmichael.  The idea of Black Power was that efforts (such as those of Martin
Luther King, Jr) to work with whites were misguided.  Carmichael believed that blacks
should work on their own, without help, to demand their rights.  He thought that
anything else would lead to black people continuing to rely on whites to give them
rights, instead of simply taking those rights for themselves.  He also believed that
King's tactics would result in less pride among Black
People.

For these reasons, A is the best
answer.