Monarch Butterflies, Whose Average Life Span is Nine Months, Migrate from the Midwestern United States to Selected Forests Outside Mexico City.

Question: 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

“Monarch butterflies, whose average life span is nine months, migrate from the midwestern United States to selected forests outside Mexico City.”- is a GMAT critical reasoning question. This GMAT Critical Reasoning topic has been taken from the book ‘501 GMAT Questions’. GMAT critical reasoning tests the logical and analytical skills of the candidates. Critical reasoning in GMAT requires candidates to find the strengths and weaknesses of the argument, or find the logical flaw in the argument. The GMAT CR section contains 10 -13 GMAT critical reasoning questions out of 36 GMAT verbal questions.

Answer: B

Explanation: This is a GMAT critical reasoning question. We have to find the option that logically completes the above passage that talks about the evidence that can be extracted by the lepidopterists.

Let’s go through each of the available options and choose the one that fits the best.

Option A: monarch butterflies have brains, however minuscule
This option is incorrect because the given theory in the passage revolves around route mapping according to the earth’s electromagnetic field and not about butterflies’ brains. Also, there is no reason for us to believe that reacting to electricity has anything to do with the presence of the brain. Since the statement is irrelevant to the passage, Option A is incorrect.

Option B: monarch butterflies are sensitive to electricity
This option is correct because the passage talks about lepidopterists taking their first step to test the theory. Once they find out that monarch butterflies are sensitive to electricity, they can further research whether it is the earth’s electromagnetic field or something else that helps the butterflies in finding their route. So, Option B is correct.

Option C: low-voltage electricity can affect butterflies, whether positively or adversely
This option is incorrect because this statement talks about butterflies and non-monarch butterflies. It does not say anything about the earth’s electromagnetic field or how butterflies got affected due to low voltage electricity. So, Option C is incorrect.

Option D: monarchs map their routes according to the earth’s electromagnetic fields
This option is incorrect because it talks about monarchs and not monarch butterflies. We cannot assume that the statement is referring to monarch butterflies. Since the statement does not say anything about monarch butterflies or their role in tracing the earth’s electromagnetic field, Option D is incorrect.

Option E: monarchs communicate intergenerationally via electromagnetic fields
This option is incorrect because finding out that they react to electrical fields is not sufficient to elaborate that they find their way back using the earth’s electromagnetic fields or communicate intergenerationally. So, Option E is incorrect.

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