The man, the dog, and the cat all sit down at the bar and the bartender says "What can I get you?" The dog looks squarely at the bartender and says I'll take a vodka, the guy will take a water, and the cat will take a scotch." The bartender looks absolutely shocked at the dog and says "This is AMAZING! You're a dog that can talk..." The guy looks at the bartender, and says "Don't be fooled, the cat is a ventriloquist."
The correct answer here is the third option.
Theme
would be the term that would best describe Twain's exploration of
social class structure, as it is exactly through the theme of The
Adventures of Huckleberry Finn that he explores. One of the major themes
of the works is the social-class in the work and it is explored through
many characters, such as Jim who is a runaway slave, Grangerfords who
are the elite, various common folk and so on.