Answer:
Because its her favorite phrase
Explanation:
I'd go with B - Article. There are hundreds of good examples for the answer being B. For example, "a book" ('a' is an article - 'book' is a noun), "an apple" ('an' article - 'book' noun). Those are just the simple ones.
The authors argument is that volunteering helps many people, not just those being directly benefited in visible ways. The author uses statistics from a study to support his/her argument.
So take this^ and add lots of info and textual support to create at least 8-10 sentences.