#21 - Specific Reference, Cannot Be True

[nutcracker]

Hi,

I'm a little lost on this one and would appreciate some help!
First, I don't see how the scenario in answer choice (E) is relevant to the hypothesis mentioned in lines 22-25. Is there an implicit connection that I missed? Or is it the irrelevance that actually makes it consistent (since we take "consistent" to mean "could be true")?
Second, I don't see why the scenario in answer choice (C) is necessarily inconsistent. In my understanding, "lose an edge" can mean losing advantage while still retaining some. If that is the case, it is certainly possible for trees with a high photosynthetic efficiency to grow more quickly than grasses with a low photosynthetic efficiency, just by a lesser degree than before. Is my analysis completely off? Thanks in advance.

[Adam Tyson]

Thanks for the question, nutcracker! The hypothesis in those lines boils down to "more CO2 may mean that the higher photosynthetic efficiency plants won't be doing better any longer". I read "losing their edge" as meaning "are no longer better off" or "no longer have any advantage".

When I am looking for something that is inconsistent with that, I want to find an example where a plant that has higher photosynthetic efficiency is still doing better than one with lower efficiency. I want to see that plant still having an edge. Answer C does that by showing us that the trees with high efficiency are doing better than the grasses with lower efficiency. The trees still have the edge, even in the CO2-rich environment. That is inconsistent with the hypothesis.

Answer E is consistent because it could be true even if the hypothesis is also correct. What is a leguminous plant? Is it one with high photosynthetic efficiency? I don't know, so there is no way to be sure that this is inconsistent with the hypothesis. If they are high efficiency and they decrease in numbers, that sounds like it might go hand in hand with the hypothesis. Maybe. The important thing is that we recognize that there is no way to prove that there is a conflict between this info and the hypothesis, so there is no way to claim that the two are inconsistent.

While we label this one as a "Cannot Be True" question, there is another way to look at this question type, and that is as a "reverse weaken" question. The info in the stimulus weakens which one of the answer choices? Which one is least likely to be correct, if that hypothesis turns out to be correct? Answer C seems to be hurt by that hypothesis, while none of the others is hurt at all, and so that is the best answer of the bunch.

I hope that helps! Keep at it!