新GRE阅读理解36套每日讨论--35（群178674184）

普渡哥

   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

普渡哥

大家快来做啊

元宝盒子

来了来了。。
C
ABC
C

xiuyuan

c
abc
c
楼主何时给答案哈~

bontravail

C ABC C

普渡哥

大家都做对了，恭喜啊