According to the dictionary a stereotype is a set of ideas that someone may have about a particular type of people, and these ideas are usually wrong or incorrect assumptions about these group of people.
The other options are not possible for the following reasons:
First, Episode refers to a single event or a group of related events. Desolation refers to a place that is completely empty and where everything has been destroyed. Finally, Blunder refers to a serious mistake usually caused by a person who has not been careful.
Could you provide the sentance that the question is talking about? You could youse dictionary.com to look it up and see if any of the definitions it gives you corresponds to the way the word is used