Fire ants from Brazil now infest the southern united States. Unlike qu

Answer is the choice that will either cause no effect on the argument or will weaken the argument.

Assumptions -
1) The imported insects are not more damaging. Make sense to assume A
2) Predator insects which are imported should be able to survive in new environment. B makes sense
3) The imported insects have to fight fire ants. So it makes sense to assume C - insects are more fierce cannot be destroyed by fire ants.
4) The last assumption is very important. If the fire ants start multiplying at a rate faster than at which they are killed - the argument is destroyed. Hence it makes sense to assume E

The only odd one is D. Even if I negate D there is no effect on the argument. There are two ways to look at D -
1) No effect on the argument. The work location of the predator insects is not the force of the argument. The effect is the force of the argument.
2) D is a scope shift. We need a confirmed method that strengthens the claim that fire ants population can be controlled. Does D affects the method? Absolutely not!

IMO D.

Moreover argument states that Ants are spreading Northwards. You would have to go beyond the scope of the passage to validate that United States is north of Brazil.

D should ne ans ... e cannot assume about location... coz no specific time frame is given

(A) The imported insects would not prove more damaging to the environment in the United States than are the fire ants themselves.
(B) The predator insects from Brazil could survive in the ecological environment found in the United States.
(C) The especially aggressive fire ants from the two-queen nests would not be able to destroy the Brazilian predator insects. these all strengthen
(D) The predator insects would stop the increase of the ant population before the ants spread to states that are farther north. <is the only one left>
(E) The rate of increase of the fire-ant population would not exceed the rate at which the predator insects could kill the ants. Again strengthen

+1 D

Premise - Fire ants from Brazil now infest the southern US. Unlike queen fire ants in Brazil, two queens in the United States share a nest. Ants from these nests are more aggressive than those from single-queen nests. By destroying virtually all insects in the nest area, these aggressive ants gain sole access to food sources, and the ant population skyrockets.
Premise - Since certain predator insects in Brazil limit the fire-ant population there

Conclusion - importing such predator insects into the United States would be of overall benefit to the environment by stopping the increase of the fire-ant population in the United States

The only way I can think of solving this question right now is “Negation” technique

(A) The imported insects would not prove more damaging to the environment in the United States than are the fire ants themselves. (Destroys conclusion when negated)
(B) The predator insects from Brazil could survive in the ecological environment found in the United States. (Destroys conclusion when negated)
(C) The especially aggressive fire ants from the two-queen nests would not be able to destroy the Brazilian predator insects. (Destroys conclusion when negated)
(D) The predator insects would stop the increase of the ant population before the ants spread to states that are farther north. (This is our answer as it does not affect the conclusion in any way)
(E) The rate of increase of the fire-ant population would not exceed the rate at which the predator insects could kill the ants. (Destroys conclusion when negated)


_________________

Fire ants from Brazil now infest the southern US. Unlike queen fire ants in Brazil, two queens in the United States share a nest. Ants from these nests are more aggressive than those from single-queen nests. By destroying virtually all insects in the nest area, these aggressive ants gain sole access to food sources, and the ant population skyrockets. Since certain predator insects in Brazil limit the fire-ant population there, importing such predator insects into the United States would be of overall benefit to the environment by stopping the increase of the fire-ant population in the United States.
Each of the following is an assumption made in the argument EXCEPT:

Conclusion - is that 1) Importing predator insects to US would be beneficial to the environment [ 2 clear assumptions - predator insects will survive the environment - (ans choice b) and second is that they themselves will not cause any damage to the environment (ans choice A) ] because predator insects will stop the increase of the fire-ant population in US [assumption - aggressive US two queen nest ants will be unable to kill these insects (ans choice c)]

(A) The imported insects would not prove more damaging to the environment in the United States than are the fire ants themselves.Clear assumption, explained above
(B) The predator insects from Brazil could survive in the ecological environment found in the United States.Clear assumption, explained above
(C) The especially aggressive fire ants from the two-queen nests would not be able to destroy the Brazilian predator insects. - Clear assumption, explained above
(D) The predator insects would stop the increase of the ant population before the ants spread to states that are farther north. - Correct Answer - The purpose of importing predotor insects is to stop increase of ant population indeed but there is not guarantee or any indication in the argument that this purpose will be achieved before ants are spread farther north up states.
(E) The rate of increase of the fire-ant population would not exceed the rate at which the predator insects could kill the ants. - If the rate of increase of fire-ant population is more than the rate at which predator insects kill those ants then the purpose of importing the predator insects is defeated. hence this is also an assumption in the argument.


Press +1 Kudos if you like my explanation

Hey guys,

For such question types, the best way forward to filter out the options by analyzing them with respect to the characteristics of an assumption.

An assumption is a pillar that supports the author's conclusion.

An assumption must bring in new information.
An assumption must be true for the conclusion to be true.

We can see that when we negated option D, it does not have any impact on the conclusion. Thus, it is not a must be true condition and is not an assumption.

Thanks & Regards
_________________

Maybe I got this twisted, but isn't the conclusion about limiting the population of fire-ants? D seems to be operating along those lines...if we negate it then the choice says that the predators WOULD NOT stop the increase...?
_________________

Hello from the GMAT Club VerbalBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________