Which of the following does not represent a primary source?

Which of the following is an example of a primary source in historical research?

When examining historical data, what rigorous steps must an investigator take if they suspect that a particular historical primary source or document might be fabricated or forged? (A) Speculate purely on the isolated psychological/mental health of the scribe who compiled the document. (B) Analyze only the physical materials (paper, ink, stone) from which the source is physically made. (C) Cross-examine and corroborate the claims made in the source with other independent, verified sources of that period.