The black sheep is an allegory for a) the impossibility to erase inequality and injustice b) the power of honesty even in the most corrupt society c) the alienation of the modern man in the workplace*** d) the inescapable greed of the rich and the powerful i chose c, can anyone confirm that? !

I would actually say A because this is not a very new phrase and signifies how someone who is a "black sheep" stands out in the flock of white sheep (or whatever a group of sheep is called) making them vulnerable to basised opinions and judgment.

I would agree with the choice, "A". 'The impossibility to erase inequality and injustice.' 

The black sheep is known for its difference in fur to white sheep. (this is basically the point of the allegory)
Our past world can be an example. African Americans were treated unequally and were not given justice until not too long ago, just because of their difference in skin color. 

I hope this helps!