The answer is: D. an aside
An aside is a comment or passage by a character in a play determined to be learned by the audience but which is not heard by the other characters in the play.
The rest of the alternatives are incorrect because a monologue is a long speech made by a character; a soliloquy is the expression of a character's thoughts and feelings, disregarding of the public; and a quotation is a phrase taken from text or speech and repeated by someone other than the original writer or speaker.
