What are the options?
A good question would be : What was the main idea?
...Elaborate please? What story? If you tell me the name of the assignment I can probably get it for you.
The correct answer that best fits the given statement above is the first option. In a Greek Drama, the purpose of the Prologue was to provide necessary backstory. It tells some earlier story and then links this to the main story. It is also the means to introduce the characters as well as their roles.
Because she is the "bad guy." Protagonist is good, antagonist is bad.