Final answer:
Without specific lines from the poem, it is inferred that the poet now understands Mrs. Long to be a great librarian, considering this would be in keeping with the nature of poetic homages.
Step-by-step explanation:
The passage in question is not provided, but based on standard interpretive approaches to literature and the options given, what the poet now understands about Mrs. Long has to be inferred from the specific lines of the poem, which are also not provided here. Given the typical contexts in which a poet would write about a librarian and the available options, it is likely that the poet has come to appreciate Mrs. Long's qualities as a librarian.
Therefore, in the absence of specific textual evidence, a careful guess would suggest that the correct answer might be C) Mrs. Long is a great librarian, especially since this option is the most positive and reflective of a typical poetic homage to someone who has made an impact on the speaker's life. Without the text, though, this remains an educated guess.