Final answer:
The correct sentence is B, which uses italics to emphasize the foreign phrase 'joie de vivre,' in line with English writing conventions.
Step-by-step explanation:
The correctly written sentence is B: Walt Whitman's poems express an amazing joie de vivre. When quoting foreign phrases that are not fully assimilated into English or when using words as words, such as in an analysis, it is appropriate to use italics for emphasis. This fits with standard conventions for integrating quotations in English writing, where it is essential to maintain grammatical integrity and clarity in distinguishing the author's voice from quoted material, as seen with Whitman and other poets.