A distemper virus has caused two-thirds of the seal population in the

Question

A distemper virus has caused two-thirds of the seal population in the North Sea to die since May 1988. The explanation for the deaths cannot rest here, however. There must be a reason the normally latent virus could prevail so suddenly: clearly the severe pollution of the North Sea waters must have weakened the immune system of the seals so that they could no longer withstand the virus.

Which one of the following, if true, most strongly supports the explanation given in the argument?

(A) At various times during the last ten years, several species of shellfish and seabirds in the North Sea have experienced unprecedented steep drops in population.

(B) By reducing pollution at its source, Northern Europe and Scandinavia have been taking the lead in preventing pollution from reaching the waters of the North Sea.

(C) For many years, fish for human consumption have been taken from the waters of the North Sea.

(D) There are two species of seal found throughout the North Sea area, the common seal and the gray seal.

(E) The distemper caused by the virus was a disease that was new to the population of North Sea seals in May 1988, and so the seals’ immune systems were unprepared to counter it.

Same passage with different stem question:  LINK

nightblade354 · Accepted Answer

A distemper virus has caused two-thirds of the seal population in the North Sea to die since May 1988. The explanation for the deaths cannot rest here, however. There must be a reason the normally latent virus could prevail so suddenly: clearly the severe pollution of the North Sea waters must have weakened the immune system of the seals so that they could no longer withstand the virus.

P: There must be a reason the normally latent virus could prevail so suddenly: clearly the severe pollution of the North Sea waters must have weakened the immune system of the seals so that they could no longer withstand the virus.
C: The explanation for the deaths cannot rest here, however

We are trying to show that a standard virus alone did not cause the deaths of all of the seals; we want to strengthen the idea that pollution, in some way, harmed their immune systems.

Which one of the following, if true, most strongly supports the explanation given in the argument?

(A) At various times during the last ten years, several species of shellfish and seabirds in the North Sea have experienced unprecedented steep drops in population. --  At first glance, this seems like an easy elimination because it talks about other animals over the decade. And that is the way you should approach this answer choice. However, once you have eliminated every other answer choice, this one stands above the rest. It is tricky because this does, indeed, strengthen our conclusion in a weak way. It shows other species going through the same process in the same area during a similar time period. And while it is a weak strengthener, it does show that this is not standalone event with the seals. There are other drops that are unexpected, meaning it can't just be the virus that has been around for a while; something else needs to be helping it. And that is why this is the correct answer. I, as stated above, will admit there is room for assumption on this (something you should never do). In all honestly, I eliminated this and then came back after going through B - E. There is no shame in doing that as long as you get the right answer! 
 
(B) By reducing pollution at its source, Northern Europe and Scandinavia have been taking the lead in preventing pollution from reaching the waters of the North Sea. --  OK, so what? At best, this is an irrelevant comment because we do not care who is taking a lead to preventing pollution (Have they actually prevented pollution? How much have they saved?). At worst, this goes against our conclusion that pollution is the cause. 
 
(C) For many years, fish for human consumption have been taken from the waters of the North Sea. --  OK, but who cares? Do the seals eat these fish (assumption we cannot make)? Have humans made such a large impact that the seals cannot survive (assumption we cannot make)? In the end, this is trying to make you think about biology and the real world. But do not bring that knowledge into a question!

(D) There are two species of seal found throughout the North Sea area, the common seal and the gray seal. --  OK, and? We have two species. This answer choice my as well have said that our seals have pink polka-dots. This information doesn't help us in any way solve the problem of whether pollution is causing our issue. If you thought that two seal populations means that one isn't effected, you have made an error as all seals are effected. Further, I think you may have lost site of the premise-conclusion relationship.

(E) The distemper caused by the virus was a disease that was new to the population of North Sea seals in May 1988, and so the seals’ immune systems were unprepared to counter it. --  This WEAKENS our conclusion. This does not strengthen it, and I am saddened that so many fell for this old trick (literally the oldest trick in the GMAT play book). You will usually see a strengthener in a weaken question, and a weakener in a strengthen question. This says that it is not the pollution, but the virus itself because it is new. Well, you just disproved our entire argument that it is pollution.

Bunuel · Answer

Official Explanation

(A) Yes.  Since presumably the distemper virus that affects seals would not affect such disparate animals as shellfish and seabirds, it is likely that another agent caused all three populations to decrease—pollution.

(B) No. This would weaken the argument. If pollution is being reduced, then pollution is less likely now to be the cause of the weakening of the seals’ immune system than in the past.

(C) No. We don’t know how this has affected the immune system of humans. If humans are becoming more susceptible to similar viruses, then it would support the argument. However, if humans are not becoming more susceptible to similar viruses, then it would weaken the argument.

(D) No. This is irrelevant. The passage is about the general population of seals. We don’t need to know the distribution of the various species.

(E) No. This would weaken the argument. If the seals’ immune system were unprepared for the new strain of virus, then the spread of the virus probably would have occurred even without the pollution

Rajen · Answer

A

(A) At various times during the last ten years, several species of shellfish and seabirds in the North Sea have experienced  unprecedented steep drops in population  --> In argument  “There must be a reason the normally latent virus could prevail so suddenly”  explains that there is something else in north sea causing deaths of shellfish (Pollution). This to some extent supports the argument
(B) By reducing pollution at its source, Northern Europe and Scandinavia have been taking the lead in preventing pollution from reaching the waters of the North Sea --> weaken
(C) For many years, fish for human consumption have been taken from the waters of the North Sea --> weaken by countering the argument with another reason 
(D) There are two species of seal found throughout the North Sea area, the common seal and the gray seal --> out of scope
(E) The distemper caused by the virus was a disease that was new to the population of North Sea seals in May 1988, and so the seals’ immune systems were ..” --- >weaken

GMATPASSION · Answer

Best is A

1)Supports: Pollution is causing others sea creatures to die as well
2) Weakens
3)Out of Scope
4)Out of Scope
5) Weakens

So Something that doesn't weakens is kind of neutral or may be supporting the Explanation.

No where it is told that we would get a perfect answer in answer choices. Relatively better is Good to choose.

Doesn't this resembles our day to day lives. We take decisions based on which is a better choice.Perfection is not always required. :wink:

YangYichen · Answer

is there anything to do with "At various times during the last ten years" I mean the past thing can have no effect on present phenomena

sayantanc2k · Answer

Unless the year when the statement is made is known, the phrase "At various times during the last ten years" does not have a role. The sentence would be more meaningful, if it were something like "during the same period".

arvind910619 · Answer

Hi folks ,

I think the answer is A 
A virus has caused the seal population to decline in north sea since may 1988 ans the decline was because of the immune system weakened by the severe pollution of the north sea.
This is a very tough problem but A provides a loose hint that strengthens the argument by giving us examples of other animals who also have suffered severe population decline .
Now the severe pollution of the north sea will affect every animal living in the zone and dependent on the north sea .So this is our strengthener

E on the other hand describes a story that does not affect the conclusion of the argument .I tells us that the virus was not native to the north sea and therefore immune system of the seals was not ready to fight the disease.It changes the reasoning of the argument .We may not know if seals will encounter the disease once if they have suffered from the disease .
So it does not strengthen the argument .

GmatKnightTutor · Answer

This was an interesting question. I do wonder, however, how people were so certain the "explanation" given in the argument referred to the author's.

There are in fact TWO explanations given in this argument:

General: A distemper virus has caused two-thirds of the seal population in the North Sea to die since May 1988

Author's: There must be a reason the normally latent virus could prevail so suddenly: clearly the severe pollution of the North Sea waters must have weakened the immune system of the seals so that they could no longer withstand the virus.

The only explanation that is specified is the former. "The  explanation  for the deaths cannot rest here, however. " Perhaps that is a bit too literal for CR, though. I guess an argument= refers to the author's view by default.

mbaaccount1234 · Answer

Hello! Regarding A, why can`t the virus be the cause of affecting animals such as shellfish and seabirds?

BinodBhai · Answer

Hi  mbaaccount1234

I have the same doubt! The stem should have clearly mentioned that this virus only affects the seals, then this answer would have made more sense and hence a better strengthener... other folks are also saying option (A) is a weak strengthener but this is all we got. A poor quality ques.

dhruva09 · Answer

Bunuel ,
Can you confirm the logic for approaching this question.

(A) At various times during the last ten years, several species of shellfish and seabirds in the North Sea have experienced unprecedented steep drops in population.

Ten years is unrelatable. So even if considered during the ten years, population declined, there could various climatic factors or any out of scope factor associated that at large can affect fauna. How to neglect that and consider this option ?

adichat2711 · Answer

Hi,
I marked B because I thought nations stepping in for pollution control over a certain area shows that there is pollution in that area in the first place and hence, strengthens the conclusion that in fact pollution has been a key factor other than the virus.

A is too vague, other species might have well died of any cause or actually the virus alone.

A distemper virus has caused two-thirds of the seal population in the

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A distemper virus has caused two-thirds of the seal population in the

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