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.