Actually, I would argue that to some extend all of them are true:
An opinion is a personal view or attitude.
-this is definitely true, it's basically a definition of an opinion
An opinion is often indicated by the use of adjectives.
-this is true! for example "my teacher is nice"
An opinion is often used as evidence in a news article.
-this is the weakest statement (but I think that it's still not false). I would however choose this as the right answer: opinion is not an evidence for anything except this opinion ( so it's valid for example for the news of "the president thinks that" if the opinion is that of the president.
An opinion has the potential to promote bias. - this is true!