随着GRE阅读考试的难度日益增加，大家需要有针对性地进行练习，本文为大家例举的就是逻辑短文的练习，文末还附有答案，供大家更好地练习。
Eight percent of the Earth‘s crust is aluminum, and there are hundreds of aluminum-bearing minerals and vast quantities of the rocks that contain them. The best aluminum ore is bauxite, defined as aggregates of alumi- 5 nous minerals, more or less impure, in which aluminum is present as hydrated oxides. Bauxite is the richest of all those aluminous rocks that occur in large quantities, and it yields alumina, the intermediate product required for the production of aluminum. Alumina also occurs natu- 10 rally as the mineral corundum, but corundum is not found in large deposits of high purity, and therefore it is an impractical source for making aluminum. Most of the many abundant nonbauxite aluminous minerals are silicates, and, like all silicate minerals, they are 15 refractory, resistant to analysis, and extremely difficult to process. The aluminum silicates are therefore generally unsuitable alternatives to bauxite because considerably more energy is required to extract alumina from them.(153 words)
4. The author implies that a mineral must either be or readily supply which of the following in order to be classified as an aluminum ore?
(A) An aggregate
(B) Bauxite
(C) Alumina
(D) Corundum
(E) An aluminum silicate
For the following question, consider each of the choices separately and select all that apply
5. The passage supplies information for answering all of the following questions regarding aluminous minerals
□A Are aluminum-bearing nonbauxite minerals plentiful?
□B Do the aluminous minerals found in bauxite contain hydrated oxides?
□C Are aluminous hydrated oxides found in rocks?
6. The author implies that corundum would be used to produce aluminum if
(A) corundum could be found that is not contami-nated by silicates
(B) the production of alumina could be eliminated as an intermediate step in manufacturing alu-minum
(C) many large deposits of very high quality corun-dum were to be discovered
(D) new technologies were to make it possible to convert corundum to a silicate
(E) manufacturers were to realize that the world‘s supply of bauxite is not unlimited
答案：C/ABC/C
上文的题目大家答对了几题？大家不仅要多做题，更要善于总结，这样才会有针对性地提高。
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