单选题 . ①Although many hypotheses have been proposed to explain why some plant communities are more susceptible than others to invasion by nonnative species, results from field studies have been inconsistent and no general theory of invasibility has yet emerged. ②However, a theory based on fluctuating resource availability could integrate most existing hypotheses and successfully resolve many of the apparently conflicting and ambiguous results of previous studies. ③The suggested theory is that a plant community becomes more susceptible to invasion whenever there is an increase in the amount of unused resources.
①The diversity in the range of resource-release mechanisms could partly explain the absence of consistent ecological correlates of invasibility. ②In particular, the theory predicts that there will be no necessary relationship between the species diversity of a plant community and its susceptibility to invasion, since nearcomplete exploitation can each occur in both species-rich and species-poor communities. ③Though Lonsdale found a positive association between species richness and invasion, this may arise from the tendency of diverse plant communities to be nutrient poor and therefore more responsive to the effects of human-caused influxes of nutrients.

11. The passage is primarily concerned with ______

A、 assessing the empirical success of a theory
B、 explaining why no consistent theoretical account of a phenomenon has been possible
C、 advocating a potential solution to a theoretical impasse
D、 deducing testable predictions from a proposed theory
E、 describing the difficulties involved in explaining certain empirical results

【正确答案】 C

【答案解析】 C：a potential solution对应作者的波动资源获得理论，a theoretical impasse对应全文第①句描述的没有统一的理论。全文主旨是支持作者的理论，而作者的理论就是用来统一这些矛盾理论的，因此选项C正确。
A：a theory对应作者的理论，但是没有对它做实验，文中未提及。
B：对应第二段第①句，属于细节。
D：文中未提及testable predictions。
E：对应第一段第①句，属于细节。