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  3. The economy in the United States is heavily dependent on aluminum, a material widely used in the construction of buildings and i

The economy in the United States is heavily dependent on aluminum, a material widely used in the construction of buildings and i

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问题     The economy in the United States is heavily dependent on aluminum, a material widely used in the construction of buildings and in making such diverse things as cars, airplanes, and food containers. In 1979 Americans used over five million tons of new aluminum, and one and a half million tons of recycled aluminum. Some ninety percent of the bauxite (矾士) ore from which new aluminum is normally derived had to be imported to meet the demand. Poorer ores are abundant in the United States, however, researchers at Purdue University may recently have found a way to obtain aluminum magnetically from these.
    Although aluminum is not attracted by ordinary magnets, under special conditions it becomes temporarily "paramagnetic", or very weakly responsive to a magnetic field. This is achieved by immersing ore particles in water to which certain salts have been added and then filtering the ore through steel wool in the presence of a strong magnetic field. It is hoped that this technique will reduce the amount of high-grade aluminum the United States must import.
In the second paragraph the word "paramagnetic" means ______.
选项 A、slightly magnetic
B、a weak magnetic field
C、a strong magnetic substance
D、the under-water magnetic power
答案A
解析 这是个词汇题。解这种题需要先找到该词所在的句子，答案往往从中可以读出。 paramagnetic在第2段首句，句子后半部分的or very weakly responsive to a magnetic field就是解释，故选A．slightly magnetic。
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