Bias is characterized by an author stating something as if it is unarguably true, when it is actually not-so-clear cut, and the author simply made some assumptions or had some experiences that supported one particular side of the argument. This is in choice A.
Choices B and C may be true but are not defining characteristics of bias, while Choice D is an entirely different fallacy altogether.
Virginia law and the government seems to take the slave as a responsible, intelligent human, while other states might not think so. The assumptions made by Virginia law about African Americans is that they should be punished for any crime they commit, likely they will get the death sentence.