The correct answers are I, II and III.
Biased means not objective and not allowing different opinions, ideas or points of view.
1. You should look for alternative viewpoints presented objectively. It means, the author should describe them in a neutral manner without judging their rights/wrongs. If you find the author bashing or criticizing someone because of a difference of opinions, the author is biased.
2. Endorsement of political or religious groups is considered as biased as it gives importance to these particular groups only. All of the presented groups on a site should be presented/ described in equal manner without stressing the position/ importance of any of them.
3. You should see if the author of the site was being sponsored / paid for writing the content. If he is sponsored, it means his objectivity is influenced and he would promote the sponsor's interests. This makes the site biased as well.