When it comes to defining the use of Jim's dialect in "The Adventures of Huckleberry Finn", we can say that his dialect projects Jim's character as a stereotype. Therefore, in this specific question the correct answer is "A".
When Mark Twain, the author, said that he did a careful job when he gave his characters their own speech, he was not kidding.
When we refer to Jim, he is a slave, and his dialogue is filled with improper words and sentences. This feature introduced by the author, also shows us a lot about Jim's education, and how he lacks the skill to pronounce some words correctly.