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Question

Difficulty: MediumWeakening Arguments

To decrease total operating expenses, the Fairview Municipal Water District plans to install bio-purification filters upstream of its primary membrane filtration system. Water district officials note that microplastic debris currently clogs and damages the delicate membrane filters, requiring $2 million annually in replacement and repair costs. Because the new bio-purification filters effectively capture over 90 percent of incoming microplastics before they reach the primary membranes, officials conclude that installing these bio-filters will significantly reduce the facility's overall annual operating costs.

Which of the following, if true, most seriously weakens the water district officials' argument?

  1. A
    The primary membrane filters deteriorate twice as fast when processing water that contains high levels of microplastic debris compared to water free of microplastics.
  2. B
    Several neighboring water districts have successfully reduced their energy consumption by switching to alternate energy sources for their pumping stations.
  3. The chemical solutions required to routinely clean and maintain the bio-purification filters cost substantially more per year than the total annual expenditure for replacing damaged membrane filters.Answer
  4. D
    The microplastics currently captured by water treatment facilities pose no known health risks to consumers at current concentrations.
  5. E
    Although bio-purification filters take several months to manufacture, the facility's existing membrane filters can remain operational until the installation is complete.

Answer

The chemical solutions required to routinely clean and maintain the bio-purification filters cost substantially more per year than the total annual expenditure for replacing damaged membrane filters.
The conclusion asserts that adding bio-purification filters will reduce overall annual operating expenses by eliminating 2millioninmembranerepairs.Thislogicreliesontheassumptionthatrunningthebio−filterswillnotgeneratenewexpensesequaltoorgreaterthan2 million in membrane repairs. This logic relies on the assumption that running the bio-filters will not generate new expenses equal to or greater than 2 million. The correct response points out that routine maintenance chemicals for the bio-filters cost substantially more per year than the $2 million saved, demonstrating that the net financial outcome will be an increase in total operating expenses, directly weakening the conclusion.

Step-by-Step Solution

1
Deconstruct the argument structure
Premise: Microplastics cause $2 million in annual damage to membrane filters. Premise: Bio-filters remove 90% of microplastics before reaching membranes. Conclusion: Installing bio-filters will reduce overall annual operating costs.
Identifying the central claim and supporting evidence reveals the underlying assumption.
2
Identify the unstated assumption
The argument assumes that the ongoing cost to purchase, operate, and maintain the new bio-filters will be significantly less than the $2 million currently spent on membrane repairs.
A net reduction in total operating costs requires that savings exceed any new expenses incurred by the plan.
3
Evaluate choices for an undermining fact
The statement showing that chemical cleaning solutions for the bio-filters cost more per year than the $2 million membrane repair bill directly breaks the underlying assumption.
If new operational expenses exceed current repair costs, total operating expenses will increase rather than decrease.

Key Concept

Evaluating Plan Feasibility and Net Cost-Benefit Assumptions
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Topics

Weakening Arguments

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