D. The narrator is bemused by Dombey's self-regard and conceited enthusiasm.
The passage presents Mr. Dombey's character in a way that highlights his pompousness, pride, and focus on his own name and legacy. The way he reveres the name "Dombey and Son" and his elaboration on the significance of it, coupled with the descriptions of his physical appearance and demeanor, suggest that the narrator finds Dombey's self-importance somewhat absurd, capturing bemusement rather than outright condemnation or praise.