Question

You should use __________ when you want to make concrete arguments, establish credibility, and emphasize the significance of your arguments. Be sure to make clear and explicit connections to your topic and to use them in moderation.

Answer 1

D). statistics. this shows that you are up to date on facts, and can prove facts about the topic you are speaking about. facts and statistics are concrete evidence that emphasize your arguments and help make your tip cohesive. 
plus it makes you come off as smarter and more credible.
-hope it helps