The correct answer is D. Page 16 of a book by author Ritter
Step-by-step explanation:
In academical writing, the MLA manual style is the document that states the parameters that should be including for writing and publishing formal academical documents, this includes in-text citations that refer to the author of a document quoting or using the ideas of an external author and source. About this, in most documents such as printed books or articles, the MLA style establishes the last name of the author and the number page in which the information appears in the original document should be included in parentheses or by mentioning the last name of the author first and the number page in parentheses at the end of the citation. Therefore, in the citation presented the number "(16)" in parentheses refers to "the page 16 of a book by author Ritter" or the page in which the information cited appears in the original document.