Answer:
The correct answer is A. Keyword, citation, or index
Explanation:
By definition, a keyword is an informational word used in an information retrieval system to indicate the content of a document with the expectation of a matching search result.
Citations are references of other authors to give credit for their ideas in the document that is prepared. Citations are used to reinforce ideas, results and data, to give points of view, examples, to deepen or amplify the arguments of the work to be elaborated.
An index lists the terms and topics covered in a document, as well as the pages on which they appear. To create an index, index entries are marked by specifying the name of the main entry and cross reference in the document, and then the index is generated.