A Forensic Documents Examiner Can Tell Someone Altered a Document

A forensic documents examiner can tell someone altered a document and determine what the document originally said:

A) if a razor blade was used to remove what a part of the document originally said.
B) if sandpaper was used to remove what a part of the document originally said.
C) if chemicals were used to obliterate portions of the original document.
D) no matter what technique was used.