The correct answer is D) The alliteration reinforces the unexpected situation of the family, creating a disappointed mood.
The alliteration in the sentences emphasizes the contrast between what the family expected and what they actually found, highlighting the disappointment and disillusionment they feel. The repetition of the initial consonant sounds in "expected opulence," "found obscurity," "promised paradise," and "found palmetto bugs" serves to reinforce the unexpected and unpleasant reality the family has encountered. Therefore, the alliteration contributes to the disappointed and disillusioned mood of the first half of "The End of an Era."