Ex8 4 求解答

lionelfengUID: 2371460

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 aluminous 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 naturally 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 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

寿伽文UID: 2997428

楼主题目看清楚啊，唉，这是摆明的陷进题啊，其实文章都不用看，怎么才能叫做铝矿。。。。。。？当然含有铝，才能称为铝矿啊

lionelfengUID: 2371460

2# 寿伽文
不看文章做阅读的风险是很大的，并且题干问的不是“什么是铝矿石”，
这道题我懂了，我第一次读题干的时候粗心了，题目里有imply，我居然还定位在“The best aluminum ore is bauxite”；
事实上，题干问的是“一种物质应该是什么或者应该容易提供什么，这种物质才能被定义为铝矿石？”
定位在
“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”
也就是说，氧化铝是产生铝的必不可少的中间环节，imply了mineral想要炼铝，都要产生或者就是alumina；这一点在最后一句：
“because considerably more energy is required to extract alumina from them” 中也有体现