The technique that Twain uses at the end of the sentence is option D, hyperbole.
Mark Twain is an author that used many humor techniques: pun, exaggerations, absurdity, irony, wordplay among others.
When he says <em>"if he even see a straddle-bug..."</em>
He is really exaggerating the situation and transforming it into an hilarious situation. He uses the reader's imagination to share personal journeys and uncommon experiences probably lived by himself.
He uses humor to represent real life situations, and as many comedians do nowadays, create characters to represent an exaggerated version of themselves.
If we try to imagine the situation expressed in the above sentence, How can we place ourselves seeing a straddle-bug? It is definitely something exaggerated, therefore, hyperbolic .
