In the ______________, the scene is set, the protagonist is introduced, and the author discloses any other background information necessary for the reader to understand the events that follow:

In literature, the writers or authors use this rhetorical device of 'exposition' to give introduction of the main character, settings, and other basic information to its audience or readers.

The writer can provide this exposition in many ways such as by adding:

Monologue- The word is derived from Greek word monologos which means speaking alone. A monologue is basically added before the starting of the play or the story in which the main character or the protagonist will be introducing its readers with flashback. So, in monologue exposition introduction is given by the main character having flashbacks.
Prologue- This word is also derived from the Greek word, 'pro' meaning 'before' and logos meaning 'speech'. A prologue is also placed before the play or the story. This provides information about the protagonist's past and takes its readers or audience to the present time. It is a piece of writing added by the writer to give a glimpse of past events and taking its readers to its present settings.
Dialogues- The author uses dialogues also for exposition by creating dialogues between the characters sharing about past events and introducing characters. In this exposition, several characters are engaged in the conversation, sharing about past events.

So, the correct answer of this fill up is exposition.