gmat prep 1

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gmat prep 1

by jainrahul1985 » Sat Jun 26, 2010 10:54 pm
To reduce the danger to life and property posed by major earthquakes, scientists have been investigating several techniques for giving advance warning of dangerous earthquakes. Since catfish swim erratically before earthquakes, some investigators have proposed monitoring catfish to predict dangerous earthquakes.

Which of the following, if true, most seriously undermines the usefulness of the proposal?

(A) In Japan, which is subject to frequent earthquakes, the behavior of catfish has long been associated with earthquakes.
(B) Mechanical methods for detecting earthquakes have not proved effective.
(C) Tremors lead to the release of hydrogen sulfide gas into water, thereby causing various fish and shellfish to behave erratically.
(D) Careful construction can reduce the dangers posed by earthquakes.
(E) Even very slight, fleeting tremors cause catfish to swim erratically

OA [spoiler]E
Can someone explain why not C[/spoiler]

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by albatross86 » Sat Jun 26, 2010 11:12 pm
Proposal is that since catfish swim erratically before earthquakes, monitoring them can be useful in predicting DANGEROUS earthquakes.

WEAKENER:


A. This establishes a historical relationship between the two and hence appears to strengthen rather than weaken the proposal.

B. This means other methods are not working. Does that mean this one will or will not work?

C. This establishes a fact that explains the connection between earthquake tremors and catfish activity. Thus it strengthens the argument that catfish activity can indicate tremors. I think maybe you thought it weakens the argument because it is the H2S that causes the activity and not the tremor itself. However, in the GMAT if A leads to B and B leads to C, we can logically bridge this to A leads to C reasonably. I have a feeling you must have thought "What if some other source of H2S is causing the erratic activity" This is actually bringing in outside info since you must only work with the information in the passage and the particular answer choice you are looking at.

D. Irrelevant. This is about predicting earthquakes and not preventing damage.

E. The key word in the proposal is DANGEROUS. This is a good example of how in the GMAT even one extreme word can break an argument. If even minor earthquakes (which we can infer are not dangerous) affect catfish, we cannot determine whether their activity is because of a minor, non-dangerous earthquake or a major, dangerous one. Hence this weakens the proposal that catfish behaviour is specifically useful to predict dangerous earthquakes.

Pick E.

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by GMATGuruNY » Sun Jun 27, 2010 3:21 am
Conclusion: To predict dangerous earthquakes, we should monitor catfish swimming.

Premise: Catfish swim erratically before dangerous earthquakes.

Assumption: Erratic swimming = dangerous earthquakes.

Predict how to weaken: Show that the erratic swimming isn't connected to dangerous earthquakes.

(A) In Japan, which is subject to frequent earthquakes, the behavior of catfish has long been associated with earthquakes. Strengthens
(B) Mechanical methods for detecting earthquakes have not proved effective. Outside scope
(C) Tremors lead to the release of hydrogen sulfide gas into water, thereby causing various fish and shellfish to behave erratically. Outside scope; argument is about only catfish, not other kinds of fish
(D) Careful construction can reduce the dangers posed by earthquakes. Doesn't weaken; studying the catfish could still help us predict dangerous earthquakes
(E) Even very slight, fleeting tremors cause catfish to swim erratically. Correct. Shows that erratic swimming doesn't equal dangerous earthquakes; the swimming might indicate only a fleeting tremor.

The correct answer is E.
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by Testluv » Sun Jun 27, 2010 8:34 pm
Can someone explain why not C
For at least 2 reasons. First, it talks about "various fish and shellfish" and we don't know whether "catfish" are included in this category or not. Second, even if catfish were included in this category, it actually strengthens the argument because it introduces a basis upon which catfish are prescient about earthquakes.
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by dustystormy » Sun Sep 11, 2016 12:55 pm
I am bumping this question as I feel E actually strengthens the argument.

@GMATGuru - you explained
(E) Even very slight, fleeting tremors cause catfish to swim erratically. Correct. Shows that erratic swimming doesn't equal dangerous earthquakes; the swimming might indicate only a fleeting tremor.

but i feel even if catfish behave erratically for slight or fleeting tremors, then its behavior acts as an indicator or warning of earthquake, which will be helpful.

Moreover, E says fleeting tremors cause catfish to swim erratically but argument says Since catfish swim erratically before earthquakes, so don't you think the two actions are after and before effects of earthquake. I am not sure if I have explained my query clearly but I think I have thought too much on this CR and now I am lost.

Experts please help.

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by MartyMurray » Sun Sep 11, 2016 2:22 pm
dustystormy wrote:I am bumping this question as I feel E actually strengthens the argument.

@GMATGuru - you explained
(E) Even very slight, fleeting tremors cause catfish to swim erratically. Correct. Shows that erratic swimming doesn't equal dangerous earthquakes; the swimming might indicate only a fleeting tremor.

but i feel even if catfish behave erratically for slight or fleeting tremors, then its behavior acts as an indicator or warning of earthquake, which will be helpful.
To get CR questions right, you often have to think reasonably.

The proposal involves monitoring catfish to predict dangerous earthquakes.

The question asks which answer undermines the USEFULNESS of the proposal.

E says that even very slight, fleeting tremors cause catfish to swim erratically.

Let's be reasonable. We can gather from E that slight tremors, even tremors not associated with dangerous earthquakes cause catfish to swim erratically. So, while yes, before a dangerous earthquake the catfish may swim erratically, in many other situations, situations that do not involve precursors of dangerous earthquakes, catfish swim erratically. So catfish swim erratically even when no earthquake is coming.

Let's be reasonable. Yes, if every time the catfish swim erratically we act as if there is an earthquake coming, we will be prepared for a dangerous earthquake. At the same time, if the catfish react to every little tremor, we will be preparing for dangerous earthquakes every time there is a little tremor. Does acting as if a dangerous earthquake is coming every time a little tremor occurs sound practical to you? So, if E is true, does monitoring catfish sound USEFUL to you?
Moreover, E says fleeting tremors cause catfish to swim erratically but argument says Since catfish swim erratically before earthquakes, so don't you think the two actions are after and before effects of earthquake. I am not sure if I have explained my query clearly but I think I have thought too much on this CR and now I am lost.
Let's keep this simple.

Catfish swim erratically before dangerous earthquakes.

Catfish also swim erratically in response to slight tremors.

Yes, it makes sense that they would also swim erratically in response to major tremors, such as the tremors of dangerous earthquakes.

That they would makes no difference though.

All we need to understand is that catfish swim erratically before dangerous earthquakes and in response to slight tremors, and so, if E is true, monitoring them may not really be useful in predicting dangerous earthquakes, because often erratic swimming is merely a response to slight tremors.
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