One Way of Decreasing the Persuasibility of Members of an Audience

One way of decreasing the persuasibility of members of an audience is:

A) to feed them desirable food while someone is trying to persuade them.
B) to forewarn them that someone is going to try to persuade them.
C) to remind them that even though the speaker might be credible, he or she may not be trustworthy.
D) to hide from them the fact that someone is going to try to persuade them.