What sets off appositives in the sentence is the use of the quotation mark, comma (,). This indicates that the phrase is just an added information in the sentence, and if omitted will never change the whole thought or idea of the sentence. Aside from commas, parentheses or dashes can be used as well.
Answer: D - include a quote c;
Explanation:
Someone close to the speaker has gone without a trace and no warning or message. The speaker is upset about this and wants to leave too because that person is gone. But the speaker wants more to stay and know more, than to leave like that person did.
Hope I helped (: