Confusing Weaken question..........OG Diagnostic test

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Guillemots are birds of Arctic regions. They feed on fish that gather beneath thin sheets of floating ice, and they nest on nearby land. Guillemots need 80 consecutive snow-free days in a year to raise their chicks, so until average temperatures in the Arctic began to rise recently, the guillemots' range was limited to the southernmost Arctic coast. Therefore, if the warming continues, the guillemots' range will probably be enlarged by being extended northward along the coast.

Which of the following, if true, most seriously weakens the argument?

(A) Even if the warming trend continues, there will still be years in which guillemot chicks are killed by an unusually early snow.
(B) If the Arctic warming continues, guillemots' current predators are likely to succeed in extending their own range farther north.
(C) Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.
(D) If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.
(E) The fish that guillemots eat are currently preyed on by a wider variety of predators in the southernmost Arctic regions than they are farther north.

OA: D

How B is wrong?

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by GMATGuruNY » Fri Aug 11, 2017 4:29 am
Mo2men wrote:Guillemots are birds of Arctic regions. They feed on fish that gather beneath thin sheets of floating ice, and they nest on nearby land. Guillemots need 80 consecutive snow-free days in a year to raise their chicks, so until average temperatures in the Arctic began to rise recently, the guillemots' range was limited to the southernmost Arctic coast. Therefore, if the warming continues, the guillemots' range will probably be enlarged by being extended northward along the coast.

Which of the following, if true, most seriously weakens the argument?

(A) Even if the warming trend continues, there will still be years in which guillemot chicks are killed by an unusually early snow.
(B) If the Arctic warming continues, guillemots' current predators are likely to succeed in extending their own range farther north.
(C) Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.
(D) If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.
(E) The fish that guillemots eat are currently preyed on by a wider variety of predators in the southernmost Arctic regions than they are farther north.
Premise:
Guillemots currently living in the southern region of the Arctic require both COLD WEATHER (since they need ICE in order to feed) and WARM WEATHER (since they need 80 CONSECUTIVE SNOW-FREE DAYS to raise their chicks).
Conclusion:
If Arctic temperatures continue to rise, the guillemots' range will probably be enlarged by being extended northward.

One assumption is that -- if the guillermots move northward -- they will also continue to live in the south.
If they do NOT continue to live in the south -- if instead they MIGRATE from the south to the north -- then their range will NOT be extended.

D: If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.
Implication:
The guillermots will no longer be able to live in the south -- since they need ice in order to feed -- WEAKENING the conclusion that their range will be extended by the warming trend.

The correct answer is D.

B: If the Arctic warming continues, guillemots' current predators are likely to succeed in extending their own range farther north.
Since CURRENT PREDATORS have not prevented the guillermot from surviving in the SOUTH, there is no reason to believe that these predators will prevent it from surviving in the NORTH.
Thus, the information in B does NOT weaken the conclusion that the guillermots' range will be extended.
Eliminate B.
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