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

Well, to be able to map, these flies need to have a brain. So, A is the logical choice.

Low voltage transmitter is not equivalent to low voltage electricity.

forgot to also include that if the flies either get attracted or repelled by the transmitter, the flies must be able to make a preference. This proves that they need to have brains.

I think C is a generalization - It talks about 'butterflies' but the issue at hand is 'monarch butterflies'. Between B and D, I'll go with D

Cheers,
Unplugged

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______

Explanation:
-----------------------
(A) monarch butterflies have brains, however minuscule ---> The theory revolves around route mapping according to the earth’s electromagnetic fields and not about butterflies’ brains.

(B) monarch butterflies are sensitive to electricity ---> This sounds right. As the passage discusses about lepidopterists taking their first step in an attempt to test the theory, this option stands as a strong contender for that first step. Once they conclude that monarch butterflies are sensitive to electricity, they might go further to test whether it’s earth’s electromagnetic fields or something else that helps monarch butterflies in tracing their route.

(C) low-voltage electricity can affect butterflies, whether positively or adversely ---> This option discusses butterflies and not monarch butterflies. Moreover, the theory focuses on the role of electromagnetic fields and not about how (positively or adversely) the butterflies get affected due to low-voltage electricity. So, option C is clearly out.

(D) monarchs map their routes according to the earth’s electromagnetic fields ---> This option goes beyond the first step of testing the theory. Moreover, it’s not monarch; it’s monarch butterflies. We cannot assume that it’s referring to monarch butterflies.

(E) monarchs communicate in intergenerationally via electromagnetic fields ---> This option too goes beyond the first step of testing the theory. Moreover, it’s not monarch; it’s monarch butterflies. We cannot assume that it’s referring to monarch butterflies.
-----------------------

I go for B.

Hope that helps.


Regards,
Technext
_________________

+++ Believe me, it doesn't take much of an effort to underline SC questions. Just try it out. +++
+++ Please tell me why other options are wrong. +++

~~~ The only way to get smarter is to play a smarter opponent. ~~~

"This option discusses butterflies and not monarch butterflies"

thanks for highlighting
is it B then?
_________________

math-polygons-87336.html
competition-for-the-best-gmat-error-log-template-86232.html

I picked B as well, and I'll add a few points to Technext's explanation:



This is really an Inference question, which means we have to think about what MUST be true if the monarch butterflies react differently to the grove with the transmitter. The larger theory is really beside the point.

(A) We have no reason to think that reacting to electricity proves the presence of a brain. Pieces of quartz react to electricity. This does not follow.

(B) This logically follows. The only thing different about the grove with the transmitter is the electromagnetic field created by the transmitter, and the monarchs react to it. They could not do that if they were not sensitive to electricity in some way or another. (Note: GMAT questions are supposed to NOT depend on outside knowledge, but this one does depend on you knowing that voltage measures ELECTRICITY, period. It doesn't measure anything else. So a "low voltage transmitter" does have to be transmitting an electromagnetic field.

(C) If the monarch butterflies respond to low voltage electricity, this DOES in fact prove that "butterflies" can respond to low voltage electricity. Monarch butterflies are butterflies, and if even one butterfly does something, then (logically) butterflies as a group "can" do that thing. But choice (C) says the electricity AFFECTS butterflies, and the facts do not show that it AFFECTS monarchs; only that they can sense it.

(D) (E) Obviously, finding out that they react to electrical fields in this limited experiment is not enough to show that they find their way all the way back using the earth's field, nor to show that they communicate intergenerationally that way. Personally, I think we can assume that "monarchs" are monarch butterflies, but it doesn't matter -- these choices are out anyway.


This has nothing to do with the GMAT, but -- how in the world do we know that the great-great-grandchildren return to the same trees? That sounds like someone had to put a lot of very tiny tags on a lot of butterflies, AND had to watch where they laid their eggs, AND tag the caterpillars, AND watch them hatch and tag them again before they flew away...
_________________

Grumpy

Kaplan Canada LSAT/GMAT/GRE teacher and tutor

About (C): I'm not assuming anything; just following the logical meaning of the words. "Can" just means "is possible". If peanuts cause allergic reactions in some people, then it is correct to say that peanuts "can" cause allergic reactions in "people", even though for most people they do not. Similarly, if electric fields did "affect" at least some monarch butterflies, then it is correct to say that electric fields "can" affect butterflies -- because monarch butterflies ARE butterflies. This remains true even if the fields do not affect all monarchs, and even if they do not affect any other species of butterflies.

About "monarchs": This is English grammar, not logic. We are able to refer back to a subclass of a noun by using the modifier only, once we have identified the subclass with both the modifier and the noun. For instance, I could start writing about "heavyweight boxers", and then refer to them as "heavyweights" for the rest of the passage. I suspect, however, that real GMAT questions might NOT use this particular grammatical structure (as this question did).
_________________

Grumpy

Kaplan Canada LSAT/GMAT/GRE teacher and tutor

I went for D thinking that is the plausible choice among all,but after reading the other posts I realized that I missed the obvious errors

choice C talks about butterflies but not about monarch butterfilies, so it is irrelevant
choice D and E says nothing about butterfiles it specifes only about monarchs so it is irrelevant ( I fell for this trap)
though choice A talks about monarch butterfliers it is neither talks about electormagnetic field nor electricity so it is out of context

so only choice B is relevant ( how easy it is to expalin after seeing the answer choice )

Powerscore CR bible says, there is a specific standard of attempting these fill-the-blank type questions. Go with the general flow of the argument, make sure the elements are duly noted and associated with each other properly, the required statement will either end up as a premise or a will be a conclusion statement.

My answer was indeed B. Btw, Low Voltage is associated with electricity only, voltage term itself should suggest that it is electricity.
_________________

I am AWESOME and it's gonna be LEGENDARY!!!