A study of fourth-graders who had eaten cupcakes showed reduced scores on math tests (Rogers 12).

In this sentence, the parenthetical information is

A. a code to the outline.

B. source citation of a paraphrase.

C. a works cited page.

D. source citation of a word-for-word quotation.

A study of fourth-graders who had eaten cupcakes showed reduced scores on math tests (Rogers 12)

The words in parentheses are an example of C, a works cited page. In other words, the information about the fourth-graders and the cupcakes comes from a book by Rogers that has already been cited earlier by the author.