Thanks for the question! So let’s take a look at the stimulus here first. We’re told that Roadwise’s ad campaign is notable for its variety. This is unusual; most people are pretty uniform. But here, we’re told, variety is a smart approach, since purchases of auto insurance are so demographically diverse.
So now we’re being asked to add the most support for the conclusion of the argument. In other words, we’re being asked to strengthen the conclusion. And what is the conclusion we’re trying to strengthen? That variety is a smart approach. So we want something that makes it more likely that variety is a smart approach.
So now look at (E), which tells us that efforts to influence a target demographic don’t pay off when the content of the ad campaign falls short. Well, this just tells us about something that results in efforts to influence not paying off. So at best, this is irrelevant, and it could also weaken. It doesn’t really strengthen the idea that “variety is good.” We can’t say that “the content of the campaign” and “variety” are the same thing. And that’s why (E) is wrong.
Hope this helps! Feel free to ask any other questions that you might have.