[求助] prep-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?

(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？

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。