The best way to describe Twain's tone in this excerpt from "Life on the Mississippi" is:
b. casual and nostalgic.
Explanation:
Mark Twain was filled with homecoming feelings that he longed endlessly to return to Hannibal, to his root, and to his boyhood friends to enjoy life on the Mississippi. When he was a young boy growing up, he had watched steamboats traversing the river with envy and unsatisfied desire. This desire propelled him to seek a seaman career to enable him work on the boats. First published in 1883, "Life on the Mississippi" chronicled Mark Twain's experiences as a steamboat pilot on the Mississippi River.
