Thinking about (D):


If these birds prey on special kind of fish, it's logical to assume, that without this fish guillemots won't be able to maintain current habitat.

So, if thin ice in southern arctics disappears guillemots will be forced to move north. It won't be the enlargement of guillemots' range, rather simply movement to better place.

between B & D, latter looks more correct as B says about extension of range of guillemots' predator but that doesn't weaken the conclusion as the argument in D. Spreading of predators will be a deterrent but if there is no food available in the southern coast they are bound to move northwards, daring the predator.

Whereas D is a better answer since it clearly refutes the concept of enlargement and imposes the idea that their dewelling has to move northwards due to lack of availability of food in south.


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my bet is C.
(C) if the birds stay in coastal region, they might still prefer staying south, because there will be even more snow-free days.

I considered A and B as well.
(A) It requires a little too much to assume. Warmer temp would bring more snow-less days, but there is no hint about an early snow.

(B) if the predators move north, birds are not gonna like it and might hesitate moving. But it is the interdependent thing, which bothers me here.

(D) not because, the birds eat on fish, which hide beneath those sheets. If that disappears, they'd definitely move north.

Hey All,

Enough questions enough that I figured it might be worth my weighing in. As any good instructor would, I'm going to focus on the passage first.

Conclusion: Warming will extend Guillemots range north

Premises: Guillemots feed on fish beneath ice, nesting nearby. Need snow-free area to raise chicks. Area is warming, particularly north.

Assumption: Something other than the warming will keep them from extending range.

We know the assumption will be this limited, because otherwise the argument is solid (i.e. if the warm area is expanding, and they can live in warm weather, then obviously their range will expand).

(A) Even if the warming trend continues, there will still be years in which guillemot chicks are killed by an unusually early snow.
Problem: This has no connection to the issue of range, because this would happen anywhere.

(B) If the Arctic warming continues, guillemots’ current predators are likely to succeed in extending their own range farther north.
Problem: In a number of answer choices here, the question is trying to trick you into thinking that the conclusion is that the guillemots will THRIVE in the new areas. But that's not the conclusion. The conclusion is merely that the range of areas in which they can survive will expand. This has no effect on that. The same predators joining them in the new area will result in much the same lifestyle the guillemots already have (same predators).

(C) Guillemots nest in coastal areas, where temperatures are generally higher than in inland areas.
Problem: This doesn't affect the conclusion, which is that the increasing temperatures ELSEWHERE will expand the range of the guillemots.

(D) If the Arctic warming continues, much of the thin ice in the southern Arctic will disappear.
Answer: This one may look out of scope, but remember that scope isn't really an issue on strengthen/weaken questions; you're allowed to bring in other information. If the thin ice disappears, then the guillemots will not be able to expand their habitat, because they survive on the fish that live under the ice. This relates to their ability to expand. To contrast with B, the predators are THE SAME in the new area or the old. In D, the food source is DIFFERENT (worse) in the new area, which weakens the conclusion.


(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.
Problem: This actually strengthens the argument, because the guillemots are planning to move north. fewer predators means a better chance of succeeding.

Hope that helps!
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Tommy Wallach | Manhattan GMAT Instructor | San Francisco

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Tussle between B and D. Actually went for B since I interpreted that since predators will be at the northern part the birds won't move there.But thats too much of assumption. Hence wrong.
OA should be D.
Great question.
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