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.
问题分析：这道题问题有较多提示，答案必须得和那个proposed method有点关系，而文中所谈的method无非就是用向日葵吸收放射性元素，我们来看选项，A围绕其他植物谈的，显然与向日葵背道而驰，排除。B 说水凉杀死了向日葵，整体意思说池塘里没有向日葵了，把原文的祖坟给刨了，留着。C 说在水中的向日葵和在地上的向日葵哪个长的更好，没提，杀。D说只有大叶向日葵能在水中长，就算有关也不是驳斥，是支持，与问题所问不符，杀。E说向日葵在不同池塘里吸收放射性元素的速度哪个更快，显然没说，杀。
