Butterflies

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Butterflies

by pankajks2010 » Sun Jun 19, 2011 5:48 am
Which of the following best completes the passage below?

Monarch butterflies, whose average life span is nine months, migrate from the midwestern United States to selected forests outside Mexico City. It takes at least three generations of monarchs to make the journey, so the great-great-grandchildren who finally arrive in the Mexican forests have never been there before. Yet they return to the same trees their forebears left. Scientists theorize that monarchs, like homing pigeons, map their routes according to the earth's electromagnetic fields. As a first step in testing this theory, lepidopterists plan to install a low-voltage transmitter inside one grove of "butterfly trees" in the Mexican forests. If the butterflies are either especially attracted to the grove with the transmitter or especially repelled by it, lepidopterists will have evidence that______

(A) monarch butterflies have brains, however minuscule
(B) monarch butterflies are sensitive to electricity
(C) low-voltage electricity can affect butterflies, whether positively or adversely
(D) monarchs map their routes according to the earth's electromagnetic fields
(E) monarchs communicate in intergenerationally via electromagnetic fields
Source: — Critical Reasoning |

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by Geva@EconomistGMAT » Sun Jun 19, 2011 5:52 am
pankajks2010 wrote:Which of the following best completes the passage below?

Monarch butterflies, whose average life span is nine months, migrate from the midwestern United States to selected forests outside Mexico City. It takes at least three generations of monarchs to make the journey, so the great-great-grandchildren who finally arrive in the Mexican forests have never been there before. Yet they return to the same trees their forebears left. Scientists theorize that monarchs, like homing pigeons, map their routes according to the earth's electromagnetic fields. As a first step in testing this theory, lepidopterists plan to install a low-voltage transmitter inside one grove of "butterfly trees" in the Mexican forests. If the butterflies are either especially attracted to the grove with the transmitter or especially repelled by it, lepidopterists will have evidence that______

(A) monarch butterflies have brains, however minuscule
(B) monarch butterflies are sensitive to electricity
(C) low-voltage electricity can affect butterflies, whether positively or adversely
(D) monarchs map their routes according to the earth's electromagnetic fields
(E) monarchs communicate in intergenerationally via electromagnetic fields
Answer seems to be D, as that is what the scientists set out to prove in the first place with this experiment. Which answer choices gave you trouble?
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by HSPA » Sun Jun 19, 2011 5:53 am
It has to be D

The geek in there is trying to produce magnetic fields out of electricity. A dynamo with no rotating parts ;)
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by pankajks2010 » Sun Jun 19, 2011 6:00 am
I had chosen C, however, the OA is B. Not sure why...

However, I doubt, its D as the scientists have just started with their first step..So, they would like to ascertain the sensitivity of butterflies to voltage and then they might relate that to earth's electromagnetic fields to be more specific.

PS: Hey Geva, may I request your views on the following post as well..
https://www.beatthegmat.com/permutation-t85448.html

Many Thanks!!
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by amit2k9 » Sun Jun 19, 2011 6:51 am
call among B,C and D.

D has been already stated in the argument.Since this is an inference based question,this option is clearly POE'ed.

C 'adversely' is the word not correctly used here.It can either attract or repel the butterflies. Hence POE.

B can be clearly inferred using the fact test.
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by pankajks2010 » Sun Jun 19, 2011 8:28 am
"Attract/Repel" ----> "Positively/Adversely"

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by sushbis » Sun Jun 19, 2011 9:42 pm
My Choice B. Since the experiment doesnt conclusively prove what the scientists wanted to prove "that the butterflies map acc to the magnetic fields", but will be a step towards that.