What examples of the following literary devices can be found in Franz Kafka's The Metamorphosis: rhetorical question, allusion, aside, sarcasm, enjambment, refrain, soliloquy, fallacy, foil, and ethos?
As we are limited in space, below are a few ideas to help get you started.
A rhetorical question is a question asked with no real intention of receiving an answer. It's purpose is to effect the reader or even emphasize a point. It can also be said that a "rhetorical question is asked when the questioner himself knows the answer already or an answer is not actually demanded" (Literary Devices, "Rhetorical Question Definition"). In either case, an "answer is not expected from the audience" ("Rhetorical Question Definition"). Instead, the question merely capture's the attention of the audience. We can actually see one very clear example of a rhetorical question in the very first chapter of Franz Kafka's The Metamorphosis. Within the very first couple of paragraphs, as Gregor examines himself to see how much he has changed during the course of the night, he asks himself, "What has happened to me?" (Ch. 1). While he might not know the exact cause of his changes, he certainly already knows what "has happened" to him in the sense that he can certainly see exactly what changes have taken place, such as his new "armored back," "brown belly [that was] divided into arched segments," etc. (Ch. 1). Hence, since he actually already knows what has happened to him, we can certainly see this as a rhetorical question geared towards emphasizing the point for the audience that something dreadful and shocking has happened.
Asides are a type of metafiction much more common and much more easy to define in drama, but asides are essentially, whether in drama or fiction, a moment of interaction between the audience and the characters, the play, or the fictional work. In plays, an aside happens when a character speaks directly to the audience while the other characters either can't or pretend they can't hear. An aside in literature commonly happens when the author interacts with the audience, or readers. For example, an author might "[appear] as a character in his (or her) novel" or, "in the midst of describing a character ... talks directly to the reader about character description itself" ("What is Metafiction"). For this reason, we more frequently see asides in the narration of a novel than anywhere else. Kafka in The Metamorphosis certainly is a very active narrator and frequently comments on his character Gregor and his odd situation. The following is one example in which the author inserts himself in the narration through commenting on the description:
When Gregor was already sticking half way out of bed--the new method was more of a game than an effort, all he had to do was rock back and forth--it occurred to him how simple everything would be if somebody came to help him. (Ch. 1)
The narrator's comment on Gregor having to make a game out of getting out of bed is certainly addressed directly to the audience/reader, making it an aside.
Enjambment is easier to speak of in terms of poetry, but it essentially happens when one phrase of text carries on past the end of a line without any pause or punctuation and has "uninterrupted grammatical meaning" ("Literary Terms and Definitions: E"). There certainly are many long sentences in the novel with phrases grammatically carrying on into the next line. The following example can be found in the first chapter:
At first he wanted to get out of bed with the lower part of his body, but this lower part—which, by the way, he had not yet looked at and which he also couldn't clearly imagine—proved itself too difficult to move.
As we can see, both the phrases "lower part of his body" and "he had not yet looked" carry on to subsequent lines, do not contain any punctuation, and have complete grammatical meaning, but of course since lines of prose can carry on until the end of a page, enjambment is much more difficult to spot and speak of in prose than in poetry because enjambment will always appear relative to the printed page.