[求助] prep-23

yangyalong

From 1978 to 1988, beverage containers accounted for a steadily decreasing percentage of the total weight of household garbage in the United States.  The increasingly widespread practice of recycling aluminum and glass was responsible for most of this decline.  However, although aluminum recycling was more widely practiced in this period than glass recycling, it was found that the weight of glass bottles in household garbage declined by a greater percentage than the weight of aluminum cans.

 

Which of the following, if true of the United States in the period 1978 to 1988, most helps to account for the finding?

 

(A) Glass bottles are significantly heavier than aluminum cans of comparable size.

(B) Recycled aluminum cans were almost all beverage containers, but a significant fraction of the recycled glass bottles had contained products other than beverages.

(C) Manufacturers replaced many glass bottles, but few aluminum cans, with plastic containers.

(D) The total weight of glass bottles purchased by households increased at a slightly faster rate than the total weight of aluminum cans.

(E) In many areas, glass bottles had to be sorted by color of the glass before being recycled, whereas aluminum cans required no sorting.

答案C，A为什么不选呢？

aircavalry

我认为关键应该理解这句：However, although aluminum recycling was more widely practiced in this period than glass recycling

aluminum虽然在范围上更广泛地运用，但是如果recycle的总量不如glass的话，总的weight还是glass会多。

C说制造商用plastic替换比aluminum更多的glass，glass减少的的总量就会大于aluminum，从而解释了finding。

A说同等size的glass比aluminum重，weight=size x amount，由于我们从前面的条件中无法推断amount，所以A不对。

[此贴子已经被作者于2007-11-22 11:29:55编辑过]

yangyalong

噢，明白了，谢谢，发现自己的思维总是跳跃性的，当时选A的原因是把自己的想法已经建立在C的基础之上了，十分感谢！

OwenBBB

注意：结论是说“回收重量升降的比列”，所以其实A选项用数学公式理解的话很容易理解的，假设今年回收a个瓶子，上年b个，所有瓶子重量为x，则文中所述的下降比列即为：（bx-ax）/bx,明显地，x是可以约去的，也就是说这个重量变化比例与单个重量无关，只与回收个数有关