Critical Reasoning

Some species of Arctic birds are threatened by recent sharp increases in the population of snow geese, which breed in the Arctic and are displacing birds of less vigorous species. Although snow geese are a popular quarry for hunters in the southern regions where they winter, the hunting season ends if and when hunting has reduced the population by five percent, according to official estimates. Clearly, dropping this restriction would allow the other species to recover.

Which of the following, if true, most seriously undermines the argument?

A.Hunting limits for snow geese were imposed many years ago in response to a sharp decline in the population of snow geese.
B.It has been many years since the restriction led to the hunting season for snow geese being closed earlier than the scheduled date.
C.The number of snow geese taken by hunters each year has grown every year for several years.
D.As their population has increased, snow geese have recolonized wintering grounds that they had not used for several seasons.
E.In the snow goose's winter habitats, the goose faces no significant natural predation.

Requesting experts GMATGuruNY and others to address why D is wrong. My reasoning was this - [spoiler]Stimulus mentions 'geese are a popular quarry for hunters in the SOUTHERN REGIONS WHERE THEY WINTER' - so if the geese recolonized a previously unused territory (away from the southern regions where hunters hunt), dropping the restriction may not benefit as much.[/spoiler] To me this choice seemed close although I preferred the OA more. I would like to know any errors in reasoning I made so that I can be aggressive in eliminating choices like these instead of contemplating.

Boiled way down the argument is as follows:

- The snow geese displace other Arctic birds.
- There is currently a law that ends hunting season once the snow geese population is decreased by 5%.
- Conclusion: If we eliminate the law, the displaced Arctic bird species will recover

The built-in assumption here is that by eliminating the law, hunters will kill more snow geese. But if they'd been killing less than 5% of the snow geese each season, then eliminating the restriction won't matter. It's only relevant if hunters wish to kill more than 5% of the population. If they'd been killing, say, 1% of the population before the restriction is lifted, there's every reason to believe that they'd continue to kill 1% of the population. This is the idea captured by B, the correct answer.

D has no real impact on the argument. The question is whether lifting the 5% rule will lead hunters to kill more snow geese, and, by extension, allow the displaced birds to thrive. If snow geese are recolonizing older wintering grounds, it's still possible that the elimination of the 5%-rule would entice hunters to kill more of them.

vidhyamurali wrote:Some species of Arctic birds are threatened by recent sharp increases in the population of snow geese, which breed in the Arctic and are displacing birds of less vigorous species. Although snow geese are a popular quarry for hunters in the southern regions where they winter, the hunting season ends if and when hunting has reduced the population by five percent, according to official estimates. Clearly, dropping this restriction would allow the other species to recover.

Which of the following, if true, most seriously undermines the argument?

A.Hunting limits for snow geese were imposed many years ago in response to a sharp decline in the population of snow geese.
B.It has been many years since the restriction led to the hunting season for snow geese being closed earlier than the scheduled date.
C.The number of snow geese taken by hunters each year has grown every year for several years.
D.As their population has increased, snow geese have recolonized wintering grounds that they had not used for several seasons.
E.In the snow goose's winter habitats, the goose faces no significant natural predation.

Premise: The hunting season for snow geese ends if and when hunting has reduced the population by five percent.
Conclusion: Dropping this restriction would allow the other species of Arctic birds to recover from the threat posed by snow geese.

One assumption is that -- if the 5% restriction is dropped -- more snow geese will be killed.

Answer choice B: It has been many years since the restriction led to the hunting season for snow geese being closed earlier than the scheduled date.
If hunters never reach the 5% threshold that would trigger the end of hunting season, then the 5% restriction has had NO EFFECT on the number of snow geese killed by hunters -- WEAKENING the assumption that dropping the restriction will reduce the number of snow geese.

The correct answer is B.

D: Snow geese have recolonized wintering grounds that they had not used for several seasons.
If the restriction is dropped, hunters could wipe out all of the snow geese at these recolonized wintering grounds, STRENGTHENING the assumption that more snow geese will be killed.
Eliminate D.

Thanks a lot, Dave and Guru. The explanations provided by both of you for B helped me understand why B is the right option. I now see why D is irrelevant.
I misinterpreted choice B as something like this -
It has been many years since the restriction was actually applied in the region on the right time (ie., when the limit was reached) - (thereby allowing hunters to hunt for a longer time). If this was the case already, then this lifting the restriction would be the same as before. Now, I understand scheduled date means 'date on which hunting season ends'.

vidhyamurali wrote:Requesting experts GMATGuruNY and others to address why D is wrong. My reasoning was this - [spoiler]Stimulus mentions 'geese are a popular quarry for hunters in the SOUTHERN REGIONS WHERE THEY WINTER' - so if the geese recolonized a previously unused territory (away from the southern regions where hunters hunt), dropping the restriction may not benefit as much.[/spoiler] To me this choice seemed close although I preferred the OA more. I would like to know any errors in reasoning I made so that I can be aggressive in eliminating choices like these instead of contemplating.

Possibly the key thing to understand here is what you seem to have done, which is something that causes many people to miss the right answers to CR questions. What you seem to have done is created a scenario that is NOT TRULY SUPPORTED by the information given in the prompt or the answer choice.

While making inferences based on what is said in CR prompts and answer choices is often necessary for finding the right answers, it's one thing to make inferences that are necessarily true based on the information given in the prompt and an answer choice and another to go beyond what is said in a way that is not necessarily true.

Your scenario, that because the snow geese are recolonizing wintering grounds they will be further from hunters, is not really supported by what is said. Is there any real reason to believe that the recolonized wintering grounds are further from hunters? In fact, you could have just as easily made the opposite argument, that because they are recolonizing wintering grounds they will be closer to or somehow more accessible to hunters. Neither is firmly based on anything that is said.

So to "be aggressive in eliminating choices like these", be careful to stick to inferring things that are necessarily true given what is said in prompts and answer choices. That way you won't start making up unsupported stories and convincing yourself that irrelevant or otherwise incorrect answer choices have validity.

If the hunting season is getting close earlier then must be that the 5% is completed by that time.Then how is is weakening?I am not able to get the reasoning here.Can u pl explain a bit more.

sandipgumtya wrote:If the hunting season is getting close earlier then must be that the 5% is completed by that time.Then how is is weakening?I am not able to get the reasoning here.Can u pl explain a bit more.

Answer choice B does not say that the hunting season has recently been closed before the scheduled date. It says that "it has been many years since" it was closed before the scheduled date, implying that in recent years it has not been closed before the scheduled date.

Now its clear.May be hurried reading caused me to overlook the intended meaning.Thanks again.