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题库 / Prep2007E1-CR-23
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?
Glass bottles are significantly heavier than aluminum cans of comparable size.
Recycled aluminum cans were almost all beverage containers, but a significant fraction of the recycled glass bottles had contained products other than beverages.
Manufacturers replaced many glass bottles, but few aluminum cans, with plastic containers.
The total weight of glass bottles purchased by households increased at a slightly faster rate than the total weight of aluminum cans.
In many areas, glass bottles had to be sorted by color of the glass before being recycled, whereas aluminum cans required no sorting.
前提：铝罐和玻璃瓶的回收利用导致家用垃圾中他们的重量减少；铝罐回收利用更普遍比起玻璃瓶；
结论：但是玻璃瓶在家用垃圾中所占的比重（和以前玻璃瓶比重占比比）比铝罐下降的更快
解释题为啥？
a.玻璃和铝罐的重量比，无关比较，原题结论是玻璃回收后和玻璃回收前的比重比.
b.扩大讨论范围，排除（原文只探讨作为饮料容器的情况下）
c.生产商会用塑料瓶取代玻璃瓶，而不取代铝罐。（给出了玻璃瓶减少的另一个途径，是塑料瓶没有的），正确
d.家庭购买的玻璃瓶的总重量增长更快比铝罐。无关比较。（购买多少玻璃都会回收利用，没有对结论产生任何意义）
e.玻璃回收前先分类，无关。（因为最后都回收，对结论没作用）
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