Which of the Following Is an Example of How Paper

Which of the following is an example of how paper documents are authenticated by distinctive characteristics?

A) when a witness testifies, "That is my signature on the letter"
B) when a writing is authenticated by its "[a]ppearance, contents, substance, internal patterns. . . ."
C) when an expert witness testifies that, in her opinion, the handwriting exemplar before her was written by the same person who presumably wrote a previously authenticated document
D) when a witness testifies, "I believe the signature on that letter is that of my spouse"