PrepTest 138, Section 3, Question 7
Researcher: Accurate readings of air pollution are expensive(73 more words not shown)
Which one of the following,(7 more words not shown)
- AMechanical monitoring devices(14 more words not shown)
- BCopper particles are(8 more words not shown)
- CExperiments have shown(10 more words not shown)
- DLichens can easily(4 more words not shown)
- ELichens absorb all(13 more words not shown)
Reading the argument
The lichens measured copper well. Can they measure everything else we need to know about the air?
At first, I'd wonder whether these organisms absorb pollutants consistently enough to be useful monitors. The experiment gives us a good answer for copper: the measurements were as accurate as those from the best equipment. Let's give the researcher that success.
But the conclusion expands from copper to pollution monitoring generally, with no information lost. What if lichens handle copper well but tell us little about another pollutant? Or what if the conditions that made this test work aren't available elsewhere? An accurate result for one substance doesn't automatically establish a complete replacement for the equipment.
What we’re looking for
To strengthen the argument, I'd most want to know that copper is representative: the same useful absorption process works for the other important pollutants too.
Working the answers
- A
An area lacking mechanical monitors might need a monitoring method. That doesn't establish that lichens can replace the information the devices would provide. Availability of the old equipment and accuracy of the proposed replacement are different questions.
- B
This gives us more places where the copper result might be useful. It still leaves us measuring copper. The conclusion covers pollution monitoring more broadly, so we need support for carrying the result over to other pollutants, not just to other locations with the same pollutant.
- C
Doing well in clean air doesn't tell us how accurately lichens measure polluted air. It also doesn't mean that they die in polluted areas; we shouldn't invent that opposite conclusion. Either way, this leaves the researcher's claim about replacing the equipment unsupported.
- D
Easy laboratory growth could make lichens convenient to supply, so this has some practical appeal. But having plenty of them doesn't show that they provide all the information the equipment provides. The key gap concerns what they measure, not simply whether we can obtain them.
- ECorrect
Now the copper result has a basis for extending to all other significant air pollutants. If lichens absorb those pollutants in a similar manner, the successful copper comparison gives us more reason to trust the broader monitoring proposal. E directly addresses the jump from one tested pollutant to the claim of replacing pollution-monitoring equipment without losing information. It strengthens that claim without requiring us to pretend every possible practical question has been settled.
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