Faden presumes, without providing justification, that the evidence for a claim has not been undermined unless that evidence
Why this is right
This is a conditional idea ("unless"), so we can diagram it and ask ourselves whether Faden made such a reasoning move: if evidence has not then evidence hasn't been proven false ? been undermined This doesn't seem tempting to me on a first glance, but ultimately since all the other answers are bad, we'd have to revisit this one and think about how it could actually work. Faden was trying to show that most of their machines were still in use one year later. Faden's evidence was a survey in which most respondents said their equipment was still in use a year later. Greenwall does try to undermine that evidence somewhat by saying, "Whoa -- can we really trust that the survey tells the truth? Isn't it possibly that many customers would lie about still using the equipment because they'd be ashamed to admit they bought the equipment and quit exercising?" Faden's final claims are trying to prove that Greenwall's objection is absurd. In other words, Greenwall was objecting to the trusthworthiness of Faden's evidence, and Faden is arguing that this objection is ridiculous, "You haven't undermined by survey evidence. Your objection is absurd. After all, you have no way of showing/proving that my survey provided false information." So, yes, we can say that Faden's reasoning was, "Since you can't prove that my survey contains any lies, then you haven't undermined the trustworthiness of my survey."
Skill tested: Flaw · how this choice captures the argument's function is the move to repeat next time.