Which of the following affects free speech?a) bad tendency doctrine b) clear and present danger doctrine c) preferred position doctrine d) all of...

The answer to this is D.  All of the options A through C
have to do with free speech.

The bad tendency doctrine and
the the clear and present danger doctrines were used to determine when speech could be
limited based on its content.  In the bad tendency doctrine, any speech that might
someday tend to lead to a bad result could be banned.  In the clear and present danger
doctrine, the bad result had to be "clear and present," meaning that it had to be a
specific danger that was likely to happen soon.

C refers to
the idea that freedom of speech, along with other fundamental rights like freedom of
religion, is to be given priority over other government objectives.  In other words, the
government needs a really compelling reason to infringe on these fundamental
rights.