The correct punctuation for the title "Happy Birthday" in the sentence is to enclose it in quotation marks, as shown in the last option Five years after landing on Mars, the Curiosity rover still roams the planet, looking for life and occasionally singing "Happy Birthday" to itself.
The sentence that punctuates titles correctly is option D: "Five years after landing on Mars, the Curiosity rover still roams the planet, looking for life and occasionally singing 'Happy Birthday' to itself."
When punctuating titles, such as the title of a song like "Happy Birthday," it is important to use quotation marks. Quotation marks indicate that the specific words are part of a title or a direct quotation.
In this sentence, the title "Happy Birthday" is correctly punctuated with quotation marks. The rest of the sentence follows standard punctuation rules, with commas separating different clauses and providing clarity to the overall meaning.
It's important to note that when punctuating titles, italics can also be used instead of quotation marks. However, in this particular sentence, quotation marks are the appropriate choice.