In the Context of a Literature Review, the Term Primary

In the context of a literature review, the term primary source refers to

A) articles relevant to your research that you identified on your own without using an index.
B) summaries of studies such as those found in the introduction section of a journal article.
C) an original research report or presentation of a theory written by the people who conducted the research or developed the theory.
D) press reports of research results in major news outlets such as the New York Times.