Answer: B. Dialogue
Step-by-step explanation:
B. Dialogue - conversation. Twain uses dialogue in the passage to show the narrator's thoughts on the different positions he wanted to occupy on the boat. He imagines how his old comrades would see him in a white apron with the tablecloth, or standing at the end of the stage-plank with a coil of rope in his hand. This dialogue is used to show the narrator's thought process and his desires for his future.