PrepTest 140, Section 1, Question 13
Animal feed should not include genetically modified plants.(41 more words not shown)
Which one of the following,(6 more words not shown)
- APotatoes are not(9 more words not shown)
- BThe rats tended(25 more words not shown)
- CIntestinal deformities at(10 more words not shown)
- DGenetically modified potatoes(15 more words not shown)
- EThe researchers conducting(27 more words not shown)
Reading the argument
Was it the genetic modification, or was it the potatoes?
The sick rats ate genetically modified potatoes. The other rats ate a normal diet. Those aren't necessarily the same foods with just one feature changed. If potatoes aren't normally in the rats' diet, switching to potatoes could matter independently of modifying their genes.
Imagine blaming genetic modification after a dog gets sick from genetically modified chocolate. We'd first ask whether ordinary chocolate would have caused trouble too. The label “genetically modified” doesn't automatically identify which feature of the food caused the problem.
What we’re looking for
That's the comparison I'd want here: modified potatoes versus ordinary potatoes, with the rest of the feeding conditions kept comparable. Instead, we have modified potatoes versus normal food. To weaken the recommendation against genetically modified plants, show that this diet change introduced another plausible explanation for the rats' problems.
Working the answers
- ACorrect
Potatoes aren't normally part of the rats' diet. That means the study changes the food itself as well as whether it is genetically modified. Perhaps eating potatoes rather than the usual foods contributed to the problems. A doesn't prove potatoes are harmful; it gives us reason to doubt that the genetic modification deserves the blame.
- B
Eating less of the potatoes toward the end doesn't establish why the rats became ill. The change in appetite could even result from feeling unwell. Without a connection between this eating pattern and the cause of the problems, B doesn't undermine the argument's explanation.
- C
Deformities present at birth are different from problems the rats developed during the feeding study. The passage contrasts problems developing in one group with their absence in the normal-diet group. A general fact about birth defects doesn't explain that difference or the weakened immune systems.
- D
Equal nutritional value doesn't mean identical effects on health. Two foods could provide the same nutrients while differing in some other harmful property. So this doesn't establish that modified and ordinary potatoes would produce the same intestinal or immune-system outcomes. It also doesn't tell us that the control rats ate ordinary potatoes; A exposes the missing comparison.
- E
Not knowing how something produces an effect doesn't establish that it doesn't produce it. Researchers could observe a reliable effect before understanding its mechanism. Here we have a reason to question whether the study isolated the cause at all, but the researchers' inability to explain a mechanism is not that reason.
More Weaken questions
Learn the LSAT our way
Our platform drills Weaken questions at your level and adjusts as you improve.