By saying "references are hardly worth the paper they are written on." (Line 6, Para.1), the author suggests that references only include ______.

A．They were attached to the cover.
B．They were written by the employment center.
C．They were written via emails.
D．They were written to the employers through fax.

A．A driving test.
B．The best way to signal.
C．A Police Movie.
D．A traffic accident.