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实在是找不到答案。。
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.
T-3-Q37.
Because mining and refining nickels is costly, researchers have developed an alternative method for extracting nickels using Streptanthus polygaloides, a plant that absorbs and stores nickel from the soil as it grows. The researchers incinerated a crop of Streptanthus they grow in nickel-rich soil. By chemically extracting nickel form the ash, they produced 100 pounds of nickel per acre of land at a total cost per pound slightly above that of current mining.
Which of the following, if true, most strongly supports the conclusion that the use of Streptanthus to extract nickel will be commercially adopted?
A. The season in which the researchers grew Streptanthus was an unusually favorable one, with the right amount of precipitation to maximize the growth rate of Streptanthus.
B. Because lowering the concentration of nickel in the soil can make land much better for agriculture in general, a plot in which Streptanthus has been grown and harvested can be sold for substantially more than it cost
C. More air pollution is generated for each pound of nickel produced by extracting it from Streptanthus than is generated using conventional mining and refining
D. The land on which the researchers planted Streptanthus was unusually free of the various weeds that can compete with Streptanthus for water, nutrients, and sunlight.
E. It is extremely rare for soil to contain higher concentrations of nickel than the concentrations present in the researchers’ experimental plot. |
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发表于 2009-11-24 01:29:10
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