PrepTest 138, Section 3, Question 9
All laundry detergents contain surfactants, which can harm(48 more words not shown)
Which one of the following,(6 more words not shown)
- ALaundry detergents that(18 more words not shown)
- BThere is no(20 more words not shown)
- CDifferent kinds of(20 more words not shown)
- DThere is reason(17 more words not shown)
- ELaundry detergents advertised(17 more words not shown)
Reading the argument
Not knowing everything about the ingredients doesn't mean we have no basis for comparing the detergents.
We know that every detergent contains surfactants that can harm aquatic life. We don't know the environmental effects of most of the other ingredients, including most ingredients in the products advertised as ecologically friendly. There may be further questions about what reaches the environment after washing. Those uncertainties are real, but the conclusion is stronger: there is no reason to think the advertised products are less damaging.
What we’re looking for
What if we have evidence that the ordinary detergents pose a greater hazard? We don't have to know every ingredient's effect to have some reason to prefer one group. That's the kind of comparison I'd look for in a weakener: information favoring the ecologically friendly products, despite our incomplete knowledge.
Working the answers
- ACorrect
This gives us a relevant difference involving something we already know can be harmful. The advertised products contain much less surfactant on average. That supplies a reason to suspect less harm to aquatic life, even though it doesn't settle the effects of every other ingredient.
Be precise: less surfactant doesn't mean no surfactant, and this doesn't prove the products are better overall. It weakens the claim that we have no reason to suppose they are less damaging. A reason for a comparison can exist before we have a complete environmental assessment.
- B
A lack of reason to think ordinary detergents' ingredients cause significant harm doesn't favor the ecologically friendly products. It gives us more uncertainty about the ordinary ones rather than a basis for saying the advertised ones are better.
- C
Different surfactants having different harmful effects could matter. But which kinds occur in which group of detergents? C never tells us that the ecologically friendly products use the less harmful kinds. Without that connection, the differences could favor either group.
- D
Other ingredients being more harmful doesn't tell us how the two groups compare. Perhaps both contain the same amounts of those ingredients, or perhaps one contains more. D identifies another concern without saying it favors the advertised products.
- E
Using more detergent could mean releasing more of its ingredients, so effectiveness is not automatically irrelevant to environmental impact. But this fact points toward a possible disadvantage of the advertised products. It doesn't give us a reason to think they do less damage, which is what would undermine the author's conclusion.
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