标题: Q23: GWD-2-Q19: 没有搜出来，大家来讨论讨论啊。 [打印本页] 作者: true 时间: 2010-3-3 20:42 标题: Q23: GWD-2-Q19: 没有搜出来，大家来讨论讨论啊。 Q23: GWD-2-Q19: Sunflowers growing in pots were placed, with their roots submerged, in the pond contaminated with radioactive elements. The sunflowers kept growing; in the process, they absorbed radioactive elements. Within twelve days, 85 percent of the radioactive elements were removed from the water, which is no less than can be accomplished with the much more expensive conventional filtration techniques. Scientists therefore propose using sunflowers for decontamination wherever there are radioactively contaminated ponds. Which of the following, if true, points to a limitation on the applicability of the proposed method of decontamination? A. Some plants other than sunflowers can also remove radioactive elements from water. B. The water in many ponds contaminated with radioactive elements is so cold that it would kill sunflowers whose roots were submerged in it. C. Sunflowers that grow with their roots submerged in water grow less well than sunflowers growing under optimal conditions on dry land. D. Only species of sunflowers with large leaves can have their roots submerged in water and still keep growing. E. In ponds in which the circulation of the water is artificially increased, sunflowers absorb radioactive elements far faster than they do in other ponds.
我选D，答案B 我觉得题目问points to a limitation，而选项D说只有宽叶的sunflowers才有题目说的功能，那么不正好说出并不是所有的sunflowers 均具有那些功能，因此不就是最好的limitation么？作者: fiaoyaya 时间: 2010-3-3 22:04
你看结论：Scientists therefore propose using sunflowers for decontamination wherever there are radioactively contaminated ponds.