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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.
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.
①aluminum回收实践的范围要比glass更广（暗示：应该aluminum在家庭垃圾中的占比下降更快）
②glass bottle在household garbage（家庭垃圾）中下降的比例更大==》注意：这里的比重就是指自身下降的重量与原来的重量比较，（现在的-原来的）/原来的，所以虽然玻璃瓶重，但是比影响比例大小
所以只可能是有其他的因素（非recycling practice）导致了玻璃瓶的大幅减少
gap：想一想，recycling是在末端减少玻璃瓶，有没有可能在生产端减少了玻璃瓶
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