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Oceanologist: Recently an unprecedented number of dead dolphins washed

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Oceanologist: Recently an unprecedented number of dead dolphins washed  [#permalink]

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New post 13 Sep 2015, 10:10
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Question Stats:

63% (02:08) correct 37% (02:34) wrong based on 345 sessions

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Oceanologist: Recently an unprecedented number of dead dolphins washed ashore along the mid-Atlantic coast. In the blood of over half of the dolphins, marine biologists discovered a brevotoxin that had been emitted by the alga Ptychodiscus brevis, in what is known as a red tide. Additionally, polychlorinated biphenyls (PCB), a toxic industrial compound, was also found in the dolphin’s blood. A reasonable conclusion, and indeed one many have drawn, is that the dolphins were simply victims of the brevotoxin. Nonetheless, brevotoxins, by themselves, are not lethal to dolphins, though they do tax the dolphins system. Furthermore, most dolphins have some accumulated brevotoxins in their blood without suffering any ill health effects. Therefore, the brevotoxins alone cannot explain the mass beaching of dead dolphins.

Which of the following, if true, does most to help explain the oceanologist’s doubt that the brevotoxins were the primary cause of the dolphins washing upon shore?

A) Most stricken dolphins that wash upon shore, whether or not they eventually die, tend to do so in the Gulf of Mexico.
B) Shortly before the dolphins washed ashore, a major oil spill not only caused algae to release brevotoxins but also released an array of deleterious industrial pollutants, including PCB.
C) While PCB can cause metabolic imbalances in dolphins so that they stop eating prematurely, the dose of PCB a dolphin encounters in the wild is unlikely to pose a lethal threat to a dolphin.
D) Scientists, near to the site of the beached dolphins, discovered a group of beach sea otters exhibiting similar symptoms as the dolphins.
E) PCB and brevotoxins exercise different effects on an organism, with PCB causing visible lesions.

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Re: Oceanologist: Recently an unprecedented number of dead dolphins washed  [#permalink]

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New post 13 Sep 2015, 10:48
though I don't disagree with option B, but option C makes more sense since, it completely eliminates the possibility PCB is responsible for dolphins being washed ashore..The question stem asks us to select an option that explains why brevotoxins were the primary cause of the dolphins washing upon shore, and C precisely does that by stating PCB is not lethal. Option B on the other hand includes additional industrial wastes; so it's not perfectly clear whether brevotoxins were lethal or the industrial pollutants..
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Re: Oceanologist: Recently an unprecedented number of dead dolphins washed  [#permalink]

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New post 13 Sep 2015, 14:54
Hi Harley1980,
Can you please explain what is the problem with answer choice C ?
Thanks in advance.
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Oceanologist: Recently an unprecedented number of dead dolphins washed  [#permalink]

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New post 13 Sep 2015, 18:06
raj44 wrote:
though I don't disagree with option B, but option C makes more sense since, it completely eliminates the possibility PCB is responsible for dolphins being washed ashore..The question stem asks us to select an option that explains why brevotoxins were the primary cause of the dolphins washing upon shore, and C precisely does that by stating PCB is not lethal. Option B on the other hand includes additional industrial wastes; so it's not perfectly clear whether brevotoxins were lethal or the industrial pollutants..


"X --> Y" but oceanologists are saying that "X didn't cause Y".

If X didn't cause Y, then what caused Y ? There must be "Z" which led to Y.

Z-->Y

Option B exactly covers that.
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Re: Oceanologist: Recently an unprecedented number of dead dolphins washed  [#permalink]

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New post 13 Sep 2015, 23:47
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subhamoycomputer wrote:
Hi Harley1980,
Can you please explain what is the problem with answer choice C ?
Thanks in advance.


Hello subhamoycomputer

Option C is a weakener because it says that PCB is ok and dolphin have it in the blood naturally. So it is possible that scientists found minimal dose of PCB that can not kill all these doplhines.

And B gives us another reason why dolphin are dead: PCB from oil spill. Answer does not says it directly but in strengthen/weaken question we need only possibility so it is ok.
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Re: Oceanologist: Recently an unprecedented number of dead dolphins washed  [#permalink]

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New post 13 Sep 2015, 23:51
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raj44 wrote:
though I don't disagree with option B, but option C makes more sense since, it completely eliminates the possibility PCB is responsible for dolphins being washed ashore..The question stem asks us to select an option that explains why brevotoxins were the primary cause of the dolphins washing upon shore, and C precisely does that by stating PCB is not lethal. Option B on the other hand includes additional industrial wastes; so it's not perfectly clear whether brevotoxins were lethal or the industrial pollutants..


Hello raj44

"The question stem asks us to select an option that explains why brevotoxins were the primary cause of the dolphins washing upon shore"

Here is wrinkle in the question:
The question asks us to "explain the oceanologist’s doubt that the brevotoxins were the primary cause of the dolphins washing upon shore"

We need to explain why brevotoxin is not the primary cause.

GMAT really likes such wrinkles and sometimes one word completely change the question so we need to read very carefully.
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Re: Oceanologist: Recently an unprecedented number of dead dolphins washed  [#permalink]

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New post 14 Sep 2015, 02:22
Oceanologist: Recently an unprecedented number of dead dolphins washed ashore along the mid-Atlantic coast. In the dolphins blood discovered a brevotoxin and polychlorinated biphenyls (PCB), a toxic industrial compound.

A reasonable conclusion is that the dolphins were simply victims of the brevotoxin.

But, brevotoxins, by themselves, are not lethal to dolphins.

addnal info: Most dolphins have some accumulated brevotoxins in their blood without suffering any ill health effects.

Conclusion: Therefore, the brevotoxins alone cannot explain the mass beaching of dead dolphins.

Which of the following explains the oceanologist’s doubt that the brevotoxins were the primary cause of the dolphins death?

A) Most stricken dolphins that wash upon shore tend to die in the Gulf of Mexico.(OFS)
B) Shortly before the dolphins washed ashore, a major oil spill not only caused algae to release brevotoxins but also released an array of deleterious industrial pollutants, including PCB.(This attacks the assumption behind the causal argument and explains the reason)
C) While PCB can cause metabolic imbalances in dolphins so that they stop eating prematurely, the dose of PCB a dolphin encounters in the wild is unlikely to pose a lethal threat to a dolphin.(This explains that PCB cannot result in dolphins death but does nothing to support that brevotoxins are not the reason for dolphins death)
D) Scientists, near to the site of the beached dolphins, discovered a group of beach sea otters exhibiting similar symptoms as the dolphins.(OFS this is regarding otters now)
E) PCB and brevotoxins exercise different effects on an organism, with PCB causing visible lesions.(Does not help in anyway)
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Oceanologist: Recently an unprecedented number of dead dolphins washed  [#permalink]

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New post 11 Jan 2018, 21:59
the pattern in B looks like a pattern in a weaken question. Nevertheless, since this question is neither strengthen nor weaken, and since the question stem is "doubt that the brevotoxins were the primary cause of the dolphins washing upon shore?" => nothing is wrong with B

Let's take another look at the question wording:

Which of the following, if true, does most to help explain the oceanologist’s doubt that the brevotoxins were the primary cause of the dolphins washing upon shore?
We can rephrase this to say:

Which of the following, if true, does most to help explain why the oceanologist does not think that the brevotoxins were the primary cause of the dolphins washing upon shore?

Well, if the oceanologist does not think that the brevotoxins were the primary cause of the dolphins washing upon shore, then the oceanologist must think that there is another cause that was the primary cause. Therefore, we need to find what the primary cause could be.

First, remember to choose an answer choice that supports the biologist's conclusion that the dolphins died NOT just from brevotoxin; some people out there do think that it was this toxin, but the oceanologist thinks it must have been something else.
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Re: Oceanologist: Recently an unprecedented number of dead dolphins washed  [#permalink]

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New post 02 Aug 2018, 18:35

Official Explanation
Answer: (B)



We are looking for an additional factor that could account for the dolphins washing upon the shore. (B) gives us such a factor, i.e., toxins released by a major oil spill.

(A) does not provide an additional factor that could account for the beached dolphins. It only discusses location.

(C) almost points at an additional factor, since PCB could help account for what happened to the dolphins. At the same time, (C) does not provide an additional factor beyond what's in the text. It does not offer an explanation as strong as the one provided by (B). The point is that the oceanologist needs something other than brevotoxins to explain the dolphins' deaths. C gives us information about PCB, but doesn't tell us anything else about how much PCB there was or whether it caused the deaths. In fact, it actually gives us information that PCB is not so bad: "the dose of PCB a dolphin encounters in the wild is unlikely to pose a lethal threat to a dolphin."

(D) does not shed any insight into a possible cause.

(E) does the opposite. It suggests that brevotoxins and PCB were responsible for the dolphins washing upon shore. Thus, it doesn't necessarily add weight to the biologists' doubts. Yes, it does say that PCB causes "visible lesions," but we don't know if lesions actually cause death in dolphins. We would have to infer this, and anytime you make this type of inference to choose an answer with these question types, you usually end up in trouble. Also, the first part of the answer choice is a bit ambiguous and doesn't necessarily show that PCB and b-toxins are killers; it only states that they "exercise different effects on an organism." For all we know, some of these effects might be good or might be bad.

FAQs: What is this question actually asking?



Let's take another look at the question wording:

Which of the following, if true, does most to help explain the oceanologist’s doubt that the brevotoxins were the primary cause of the dolphins washing upon shore?
We can rephrase this to say:

Which of the following, if true, does most to help explain why the oceanologist does not think that the brevotoxins were the primary cause of the dolphins washing upon shore?

Well, if the oceanologist does not think that the brevotoxins were the primary cause of the dolphins washing upon shore, then the oceanologist must think that there is another cause that was the primary cause. Therefore, we need to find what the primary cause could be.

I don't understand why (B) is the correct answer. The question is asking for me to provide support for the fact that brevotoxins couldn't be the sole cause of the dolphins' death. However, (B) does not do this.

First, remember to choose an answer choice that supports the biologist's conclusion that the dolphins died NOT just from brevotoxin; some people out there do think that it was this toxin, but the oceanologist thinks it must have been something else.

It's understandable to be hesitant to choose (B), since it seems like something that was already said in the passage. But actually, (B) does add more detail, and thus support, to the biologists' doubt. Choice (B) not only gives us a source of both the b-toxin and the PCB, but we are also told that other "deleterious industrious pollutants" were released. PCB is just one of them. So this answer choice doesn't really repeat what's been said.
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Re: Oceanologist: Recently an unprecedented number of dead dolphins washed &nbs [#permalink] 02 Aug 2018, 18:35
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