Which of the following is a characteristic of dramatic irony?

Dramatic irony is a literary device commonly used in plays and literature where the audience has knowledge that a character does not. This creates a tension or additional layer of meaning, as viewers or readers are able to see the disparity between the character's understanding of a situation and the reality. For example, in a play, if a character plans a surprise party for someone who is already aware of it, the audience knows that the surprise will not have the desired effect, leading to a deeper engagement with the unfolding events.

The other options refer to different literary concepts. A character speaking alone on stage is known as a monologue, which does not involve an audience's prior knowledge influencing interpretation. A repeated refrain is a feature of poetry that emphasizes a theme or emotion but does not relate to the relationship between the audience's understanding and a character's ignorance. Lastly, concluding remarks of an argument pertain to the structure of persuasive writing or speaking, which is distinct from the narrative device of dramatic irony.