The Iceman wrote: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.

IMO : B

Ok...so what we have here is the resolve the paradox question.

Recycling of Beverage containers (Al+Glass) accounted for a steadily decreasing percentage of the total weight of household garbage.

Although Al recycling > Glass recycling

Wt of Glass bottles in garbage < Wt of Al Bottles

Here, the author assumes that if Al bottles are being recycled more then their weight in garbage should be less and not otherwise. She assumes that it's the recycling that must absolutely contribute to the reduction in weight and not some other factor.

We need to find that some other factor which is causing this "otherwise".
We need to find the answer that - Why did the weight of Glass bottles decrease??

Proceeding in this direction, one can quickly eliminate A, B, D and E.

A - If glass bottles are heavier and recycling is less, weight should have increased. We need an answer to the question that why did the weight decrease?
B - if a significant fraction was glass bottles + other glass products, weight should have increased. Moreover, we are not concerned about type of products. We have a question to answer i.e. why did the weight decrease?
D - Says that the weight has increased. But we are arguing that why did the weight decrease?
E - Sorting is out of scope here.

C is the only option that tells us why did the weight of Glass bottles decrease in-spite of less recycling.

Although I have my reasons but I'm not sure if my reasoning is correct. Please build up my confidence by sharing official answer.

charu_mahajan wrote:A - If glass bottles are heavier and recycling is less, weight should have increased. We need an answer to the question that why did the weight decrease?
B - if a significant fraction was glass bottles + other glass products, weight should have increased. Moreover, we are not concerned about type of products. We have a question to answer i.e. why did the weight decrease?

Please check your line of reasoning for options A and B.

For evaluating option A

Let's suppose that for the same size each glass bottle weighs 100 kg and each Al bottle weighs 1 kg.

So, even if recycling of glass is less than Al, it could mean more kgs of glass being deducted from the garbage.

But remember that this is not the point here. We are interested in %age change of each type. So if there were 500 kgs of glass (5 glass bottles) and 8 kgs of Al (8 cans), we may have a case where if only 1 glass bottle were removed the %change for glass is 20% and if 4 Al cans were removed % change for AL is 50%. This is just opposed to the actual finding in the argument. Ofcourse we can also show, playing with the numbers, that glass bottles in household garbage declined by a greater percentage than the weight of aluminum cans.

Eliminate A.

For evaluating option B

Even if recycled glass bottles contained anything other than beverages, how does this matter?

Anyways when we recycle those glass bottles, we do that without beverage or any other stuff inside it. Also we do not care about the shape and size of the bottle. The most we could care about is the weight (if at all it were mentioned), which would still be irrelevant here as is the case in option A.

Eliminate B.

Rest is cool!

And yeah, the OA indeed is C

I knew I was a little offtrack here. Thanks for the explanation.