The correct answer is D. Providing evidence indicates that the person understands the issue, carefully thought about his or her position, and then found supporting research to defend that position in an effort to convince the audience. It is always important to provide evidence to support your arguments, because otherwise, your arguments won't be credible. You cannot expect anyone to believe you if you don't prove to them why they should believe what you have to say. This is why providing evidence is extremely important, especially in a debate.
