(d) The requirement is to identify the encryption feature
that can be used to authenticate the originator of a document
and to ensure that the message is intact and has not been
tampered with. Answer (d) is correct because digital signatures
are used in electronic commerce to authenticate the originator
and to ensure that the message has not been tampered with.
Answers (a), (b), and (c) are all incorrect because they do not
directly deal with such authentication.