In life on the mississippi, which best describes the difference between the language of the narration and the language of the dialogue?

The difference between the language of the narration and the language of the dialogue is that (A) Twain uses regional dialect in the dialogue, which highlights the fact that he has grown and changed since he worked on the river.

Here are the following choices after a thorough research:
A. Twain uses regional dialect in the dialogue, which highlights the fact that he has grown and changed since he worked on the river.
B. Twain uses regional dialect in the dialogue, which reinforces his embarrassment about his past job on the river.
C. Twain uses regional dialect in the narration, which illustrates his desire to return to his job on the river.
D. Twain uses regional dialect in the narration, which demonstrates that he has retained all the knowledge he learned on the river.