Answer:
1. Dialects
2. Credible
3. Realist
Explanation:
The Adventures of Huckleberry Finn by Mark Twain is set in the Southern United States, along the Mississippi River, in the antebellum era, which is the period from the late 18th century until the start of the American Civil War in 1861.
So, by the use of dialect ("pretty neat", "couldn’t a"m, "he woulda", "brung up to it."), the author archives to capture the essence of people that lived in the South at that time period. Likewise, he used this technique to make the story more credible, which is one of the main characteristics of realist literature in America, which was characterized for the depiction of social realities and lives of ordinary people as they were, without embellishing them.