From 1978 to 1988, beverage containers accounted for a steadily decrea

The question asks us to "account for a finding," so let's take a look at the exact "finding" in the passage:

There is a discrepancy between this finding and the fact that "aluminum recycling was more widely practiced than glass recycling." This fact would otherwise lead us to expect the weight of aluminum cans in the trash to decrease by a greater percentage than that of glass bottles, because cans that are recycled would not end up in the trash.

Our task is to find an answer choice that explains the discrepancy between the finding and the evidence. Let's go through the answer choices:


The finding in the passage deals with change in the percentage of weight of both items. Even if glass bottles are heavier than aluminum cans, you would still expect their weights to be reduced proportionally -- so if aluminum cans are recycled more, you would expect the weight of aluminum cans in the trash to decline more by percentage than the weight of glass bottles.

Answer choice (A) would be relevant in studying the change in total weight of these materials, but not so much for percent of weight. This factor does not explain the discrepancy in the change of percentage of weight. Answer (A) is out.


If you look back at the "finding" in the passage, it does not mention beverage containers at all. We are concerned only with the weight of glass bottles and aluminum cans in the trash by percentage. The contents of those glass and aluminum objects are irrelevant to the conclusion, so answer (B) is out.


This is more like it. We need a reason for a greater decline in percentage of glass bottles in the trash than aluminum cans in the trash, and answer (C) gives us a good reason. Households replaced "many" glass bottles with plastic containers, while only replacing "few" aluminum cans with plastic. So fewer glass bottles would end up in the trash despite more aluminum cans being recycled. This accounts for the discrepancy between the evidence and finding.

(C) is looking great, but let's finish up the other answer choices.


We are looking for a reason that the percentage of weight of glass is lower than expected when compared to that of aluminum. Answer (D) states that household purchases of glass bottles is increasing faster than purchases of aluminum. This is the opposite of what we need to resolve the discrepancy, so answer (D) is out.


This answer might explain why aluminum recycling is more widespread than glass recycling, but it has nothing to do with the central discrepancy we are trying to resolve: why did the percentage of weight of glass decrease more than that of aluminum?

Answer (E) is out, and answer (C) is correct.