Final answer:
'Alone' fits best as an 'exposition', which introduces background information in a story, whereas a 'prologue' is specific to a tragedy that comes before the Chorus's Parode.
Step-by-step explanation:
"Alone" can be best identified as an exposition. In terms of a tragedy, the prologue is the part which precedes the Parode of the Chorus, introducing the story and characters.
Meanwhile, the exposition is more broadly a literary device used to introduce background information about events, settings, characters, or other elements of a work to the audience or readers. The term 'prelude' may also be used to describe an introduction to a larger piece, but within the context of tragedy and the options given, 'exposition' is the most apt choice.