BTGmoderatorRO wrote:To process waste more efficiently, the city of Hayfield plans to revise disposal methods for residual waste, which is waste from households that contains recyclable materials that have not yet been processed separately. Residual waste typically contains a mixture of biodegradable materials as well as hazardous toxins. Hayfield plans to use the latest waste-to-energy technology to convert the biodegradable materials from residual waste into energy, thereby making the most efficient use of such waste products.

Which of the following most strengthens the given plan?

A) The quantity of residual waste generated by the city is greater than that of any other kind of waste.
B) Biodegradable materials consist of over three-fifths of the total annual amount of residual waste in Hayfield.
C) Toxins found in waste products are not indistinguishable from non-toxic materials.
D) The latest waste-to-energy technology can also be used to recycle discarded materials other than residual waste.
E) The amount of waste generated by Hayfield's industrial regions is among the highest anywhere in the country.
OA is c
why is C the correct answer? any explanation?

I am happy to help. This is a Plan question type. In a Plan question, the GMAT will give us a plan and ask us to Weaken/Strengthen the plan. In all Plan questions, the most crucial step is to identify the Objective/Goal for which the plan is designed. Once the goal is identified, there are 2 ways to strengthen a plan, namely:

1.show that the plan would meet the goal/objective
2.show that the plan can be easily implemented

To weaken a plan, we have to show that the plan wouldn't meet its objective.

In this case, our plan and goal are as follows:

Plan: Use the latest waste-to-energy technology to convert the biodegradable materials from residual waste into energy
Goal: Make the most efficient use of residual waste

Seems like a great plan! Convert the residual waste into energy using the latest state-of-the-art technology. However, as is the case in any CR question, we want to think about what could be a potential flaw/problem with this plan? Well, we want to make the most efficient use of residual waste - however, we want to convert only the biodegradable component to energy. The problem with residual waste is that it typically contains a mixture of biodegradable waste AND TOXINS! Presumably, we wouldn't want to convert toxins to energy - this would be a totally futile, possibly life-threatening use of residual waste.

Therefore, in order to make the most efficient use of the waste, we have to be able to separate the biodegradable part from the toxic part since we are really interested in converting ONLY the biodegradable component to energy. This is what Option C addresses.

C. Toxins found in waste products are not indistinguishable from non-toxic materials - A double negation - 'not indistinguishable' - is one of GMAT's favorite constructions on the higher-level CR and RC questions. Always change a double negation to an affirmative - it is much easier to comprehend the sentence. Option C essentially reads "Toxins found in waste products are distinguishable from non-toxic materials". In other words, we can use the technology to identify and convert only the BIODEGRADABLE component.

Let us go through the other options:
A) The quantity of residual waste generated by the city is greater than that of any other kind of waste - Good, but will we be able to make efficient use of this residual waste? This option doesn't address this question. Eliminate
B) Biodegradable materials consist of over three-fifths of the total annual amount of residual waste in Hayfield - Same as A. Eliminate
D) The latest waste-to-energy technology can also be used to recycle discarded materials other than residual waste - Out of scope; Waste other than residual waste is beyond the argument. Eliminate
E) The amount of waste generated by Hayfield's industrial regions is among the highest anywhere in the country - Same as A. Eliminate

Hence, C is the correct answer.

Please let me know in case anything doesn't make sense.