#3 - Fire ants from Brazil now infest the southern United

[Administrator]

Complete Question Explanation

Assumption-X. The correct answer choice is (D)

The stimulus introduces a problematic situation and offers a solution. The situation is that fire ants from Brazil now infest portions of the US and are extremely destructive to native insects.

The argument is that since certain predator-insects in Brazil limit the fire-ant population there, importing those predator-insects to the United States would be a good way of controlling the fire-ant population in the US, and of overall benefit to the environment.

The argument makes several assumptions. First, it assumes an analogy between the situation in Brazil and that in the US. Will the predator-insects be able to control the fire ants in the US, or will the altered environment limit the predators' abilities? The argument forgets to discuss that. Also, the argument does not consider that the predator-insects might actually make the problem in the US even worse. If those insects are aggressive enough to control the fire ants, what impact will those predator-insects have on the native insects that are, so far, managing to survive? It is not at all clear that importing the predator-insects is a good idea.

Basically, the argument assumes an analogy between the US and Brazil, which is vulnerable to the introduction of more evidence, so it is likely that assumptions will defend the argument from harmful potential evidence.

This is an EXCEPT question, so you will eliminate the assumptions.

Answer choice (A): This choice defends the argument from the possibility that the predator-insects are even worse than the fire ants, so this is an assumption the argument makes, and this response is incorrect.

Answer choice (B): If the predator insects are not able to survive in the US, bringing them to the US wouldn't hurt anything, but it would be a complete waste. This is a consideration the argument needs defense against, so this response is an assumption, and this choice is wrong.

Answer choice (C): This choice defends the argument from the possibility that the especially aggressive fire ants in the US might actually be vicious enough to destroy the predator-insects. If the predator-insects are destroyed by these nasty fire ants, they won't help solve any problems, so this choice is an assumption and is wrong.

Answer choice (D): This is the correct answer choice. At first glance, that might seem confusing, since it makes it more likely that the predator insects would stop the expansion of the fire ant populations. However, it doesn't show that the predators won't be more harmful than the fire ants, and the assumption negation technique can show that this response is not essential. The conclusion was that the environment would experience overall benefit, and that the increase in the population of fire ants would be stopped. If the predator insects don't stop the increase before the ants spread, there could still be a benefit to the environment, and the increase could still be stopped at some point, so this choice fails the negation test, is not necessary to the argument, and is a correct response to an except question.

Answer choice (E): If the fire ants reproduce more quickly than the predator-insects can eat them, the predators might not be able to control the fire ant population. Since this choice defends against that possibility, it is an assumption, and this response is incorrect.

[AnnBar]

Hi,

Could you walk me through the negation of the of answer choice D?

The version I had was " The predator insects would NOT stop the increase of the ant population before the ants spread to states that are farther north." I then looked at the conclusion: "...overall benefit to the environment by stopping the increase...". It seems the answer choice once negate attacked the conclusion ( increase would not be stopped, while the conclusion is claiming the overall benefit by stopping the increase)..

Thank you,
AB

[Steven Palmer]

Hi Ann,

You're right in how you negated Answer Choice (D), but a little off on how you applied it I think. Think about how the person who wrote the stimulus would respond to our attack of "The predator insects would NOT stop the fire ants from spreading to the North." She could easily answer that by saying, "Well, sure they won't stop the fire ants from going North but they'll still stop them! AND overall, that will help the environment."

Thus, we don't need to predator insects to stop the ants before they go North, just stop them at all and help the environment in doing so.

Hope this helps!
Steven

[onlywinter]

I answered D but have a question about C. Does destroy mean completely kill off? Is the "the" in "the Brazilian fire ants" synonymous with "all?" I wasn't sure if I should take C as meaning that the fire ants will completely kill off all the Brazilian predator insects or if they woulf just kill some of them. If it's the former, then I believe this is a good assumption. If it's the latter, then I believe the assumption is false.

[James Finch]

Hi Onlywinter,

(C) is referring to the fire ants killing off all of the predator insects. When no quantitative modifier term is given ("few," "some," "many," "most," etc.), we can assume that all of those things are being referred to.

Hope this helps!

[onlywinter]

Thanks for confirming!

[whardy21]

I chose B. My prephrase was the the correct answer will not be necessary to the argument if the conclusion is valid. I don't understand how D is correct. I thought answer choice B was irrelevant and not necessary to the argument.Thank you please explain.

[Adam Tyson]

Try negating answer B, whardy21 (which means make that answer false). You should then get "The predator insects from Brazil could NOT survive in the ecological environment found in the United States." If the predators cannot survive in the U.S., then they will not be able to limit the fire ants in the U.S. and solve the problem there. The environment would not benefit by bringing in a bunch of predators that die instead of living and preying on the fire ants.

For answer D, what if "The predator insects would NOT stop the increase of the ant population before the ants spread to states that are farther north"? So what? The fire ants could move north, and then the predators could come in after them and deal with them, benefiting the environment. It doesn't matter when the predators arrive, as long as they benefit the environment when they get here (and to do that, they have to be alive to do their job).

I hope that clarifies things for you! Keep at it!

[annabelle.swift]

I'm confused on how E affects the stimulus conclusion.

I negated E to say "The rate of increase of the ant population will exceed the rate at which the predators could kill the ants." From this negation, I thought that the increase in the ant population would slow down, but not stop.

This would contradict/attack the second part of the stimulus conclusion ("by stopping the increase of the fire-ant population." However, I thought that even a slowing down of the increase in the ant population would still be a benefit to the environment. Thus, I thought that E did not fully attack the argument and may not be an assumption.

Where did my thinking go wrong?

[Robert Carroll]

annabelle.swift,

You showed that the negation of answer choice (E) contradicted the conclusion. That proves that answer choice (E) is an assumption necessary for the argument. Even if the slowing down is a benefit to the environment, the conclusion statement that there would be an overall benefit by stopping the increase would be completely refuted. That would show the conclusion false. It's not a partial undermining of the conclusion - the conclusion is that entire statement. If part of it is false, it's all false.

Robert Carroll