Answer :

Bias means when someone uses favoritism. When you are being unfair by making your opinion make you chose a certain options. For example, someone was asked to chose a contestant on a dance competition by their turns and facial expression. You saw the one of the two contestants earlier before the competition and they said said "THAT is the judge?" woah there are old. That made you upset so you chose the other contestant because you were mad. If you make your own opinions about something you are comparing then you are not being fair about one subject you talk about in Comparison and Contrast. 

Hope this helps you out! #UrWelcome