In the last few years, a drastic spike in sea temperatures around Prud

Question

In the last few years, a drastic spike in sea temperatures around Prudhoe Bay has caused the eggs of snow crabs to hatch earlier in the year than they had previously. As a result, baby snow crabs are more likely to be caught by deep sea fishing boats, since deep sea fishing boats are more numerous in Arctic waters during the fall season than they are during the winter season.
 
Which of the following pieces of information is necessary to evaluate the argument?

A) The total number of snow crabs that hatch versus the total number that had hatched before the increase in temperature

B) The time of year the deep sea fishing boats arrive to the waters around Prudhoe Bay

C) The month in which the boats leave, and the month in which the snow crabs eggs hatch

D) The amount of area the fisherman’s nets can cover in one day

E) The amount of time the deep sea fishing boats spend in water directly above where the snow crabs are likely to hatch

IanStewart · Accepted Answer

We know the fishing boats are there in the fall. But we also need to know something about the snow crabs. All we know is that the snow crabs are now born earlier than before. But we have no clue what that means - does that mean they're born in May instead of July, or in October instead of December? Without that info, we can't tell if the boats and snow crabs will be present simultaneously, so C is the answer.

It also seems to me it would be useful to know if Prudhoe Bay is in the Arctic, because if it's not, the argument wouldn't make sense. But that's not in any of the answer choices.

It also seems to me it would be useful to know if Prudhoe Bay is in the Arctic, because if it's not, the argument wouldn't make sense. But that's not in any of the answer choices.

JarvisR · Answer

In the last few years, a drastic spike in sea temperatures around Prudhoe Bay has caused the eggs of snow crabs to hatch earlier in the year than they had previously.
As a result, (Conc:) baby snow crabs are more likely to be caught by deep sea fishing boats, since deep sea fishing (Premise)boats are more numerous in Arctic waters during the fall season than they are during the winter season.

Which of the following pieces of information is necessary to evaluate the argument?

A) The total number of snow crabs that hatch versus the total number that had hatched before the increase in temperature
>>not sufficient.
B) The time of year the deep sea fishing boats arrive to the waters around Prudhoe Bay
>>Time of year is immaterial here as we dont know the same abt the eggs.
C) The month in which the boats leave, and the month in which the snow crabs eggs hatch
>>This one is important to ensure that they don't return empty handed.

D) The amount of area the fisherman’s nets can cover in one day
>>Not relevant/ doesn't help much
E) The amount of time the deep sea fishing boats spend in water directly above where the snow crabs are likely to hatch
>>Same as D. Doesnt help much.

D) The amount of area the fisherman’s nets can cover in one day >>Not relevant/ doesn't help much E) The amount of time the deep sea fishing boats spend in water directly above where the snow crabs are likely to hatch >>Same as D. Doesnt help much.

apoorv601 · Answer

C
Conclusion -baby snow crabs are now more likely to be caught by deep sea fishing boats
premise - bc of changes in temperature during the yr, the snow crabs to hatch earlier 
Knowing the boats  leaving  month as compared to the hatching month of the eggs is necessary for evaluating conclusion

romeotc · Answer

I would somewhat agree with this comment. In fact, I think that if we don’t know the position of PB with regards to the Arctic, the correct answer choice would be either B or C.
Let me explain:
If Prudhoe Bay (PB) is a region next to the Arctic, or even if PB is a region at the center (or another place) in the very huge Arctic (and boats must travel through other areas of the Artic before they can get to PB), then let’s consider option B: 
For B: The time of year the deep sea fishing boats arrive to the waters around Prudhoe Bay 
The question only gives info about “deep sea fishing boats are more numerous in Arctic waters”, not “around Prudhoe Bay” where snow crabs eggs hatch. So the boats may arrive in Arctic in fall, but if they arrive to the waters around Prudhoe Bay in the winter, then the conclusion will be weakened. But if they arrive to the waters around Prudhoe Bay in the fall (the same time they arrive at the Arctic), then the conclusion still holds true. 
So knowing “The time of year the deep sea fishing boats arrive to the waters around Prudhoe Bay” would either make or break the conclusion, then B is also the right answer choice. 
This question is therefore a little controversial, I think.
Of course, some people might say that the knowledge about “the location of PB with regards to the Arctic” should be “common knowledge” and GMAT expects that we all know this, but I wouldn’t agree with such comment. For me, “where China is” may be considered as “common knowledge”, but things about “the location of PB with regards to the Arctic” is not “common knowledge” at all (even geologists may not know all the corners/geo names of the world, how are we supposed to know?).

Posted from my mobile device

Mahmud6 · Answer

Hi Expert,

Would you please explain how C is correct and B is incorrect?

abhimahna · Answer

Hi  Mahmud6  ,

Here I go:

The argument is saying Increase in temp caused the eggs of snow crabs to hatch earlier. Then it says as a result, probability of getting caught by boats has increased because more boats are there in fall season.

We need to evaluate what author concluded.

Now, let's talk about B and C.

B) The time of year the deep sea fishing boats arrive to the waters around Prudhoe Bay -->  The author has already stated that more boats are coming in fall. We need to find out how this time is related to crabs. We don't have any information about crabs here. Let's say if I say boats are arriving in June of every year. But how does that tell us crabs would be caught or they would be able to skip from getting catched. In order to weaken/strengthen what author said, we need relevant information about both. Hence, Incorrect.

C) The month in which the boats leave, and the month in which the snow crabs eggs hatch -->  Now it may happen that Both arrive in the same month. This means the conclusion is strengthened. But what if Boats arrive one month before eggs hatch? In this case, the conclusion made by author is weakened. Hence, the correct answer.

Does that make sense?

Mahmud6 · Answer

C

My reasoning

Let, snow crabs usually hatch in Winter (from December to February), but because of rising sea temperature, snow crabs hatch earlier, i.e. in late Fall (November). On the other hand, deep sea fishing boats are more numerous in Arctic waters during the fall season (from September to November). So, if all deep sea fishing boats leave within mid-fall (October), then baby snow crabs are NOT more likely to be caught by deep sea fishing boats, but if all deep sea fishing boats stay until winter, then baby snow crabs will more likely to be caught by deep sea fishing boats.

aragonn · Answer

Official Explanation
Answer: (C)

The question asks us to evaluate the argument. We need to decide what information is needed in order to tell whether or not the argument is valid.

Conclusion: crabs are hatching earlier due to an increase in sea temperature. Therefore, the baby crabs are more likely to be caught by deep sea fishing boats. To evaluate the argument, we have to know when the fishing boats are there. That is, if the crab hatches earlier, but the fishing boats have already left, then the conclusion cannot be drawn. Essentially, are the crabs hatching in the fall when the fishing boats are present?

(C) provides us with the necessary information to draw the conclusion: are the crabs hatching when the fishing boats are still there.

(A) is wrong because it does not relate to the fishing boats.

(B) is tempting. The paragraph already implies that they are there in the autumn. If we know the month they arrive, that still doesn’t tell us anything about the crabs.

(D) is irrelevant, since we are not concerned with the efficiency of the fisherman’s nets.

(E) indirectly gives us some information on whether the fisherman are going to catch more crabs than if they were not directly above where the crabs hatch. But it doesn’t address the fundamental gap: will the fishing boats even be there when the baby crabs hatch.

Alilee · Answer

Argument: baby snow crabs are caught by deep fishing boats since they are hatching early due to increased tmepeture. 
Goal: Evaluate Q

A) The total number of snow crabs that hatch versus the total number that had hatched before the increase in temperature
 Irrelevant. Knowing this info doens't help us evaluate the argument 
B) The time of year the deep sea fishing boats arrive to the waters around Prudhoe Bay 
 We already know this <- fall time  
C) The month in which the boats leave, and the month in which the snow crabs eggs hatch 
 CORRECT. We know when the boats are here from teh passage but don't know when the eggs hatch. knwoing when the eggs hatch will help use determine if there even is an overlap in timing between the hatch time and boat presence.

egmat · Answer

The Core Logic: 
The argument claims: Earlier hatching → More baby crabs caught by boats

For this to be true, one thing must happen:  crabs must hatch WHILE boats are still present .

This is a question about  timing overlap  between two events:
 1.  When baby crabs exist (after hatching)
 2.  When fishing boats are in the water

Why B is Insufficient: 
B tells us when boats  arrive . But arrival time alone doesn't tell us when boats  leave .

Here's the trap:  Suppose boats arrive in September and leave in October, but crabs now hatch in November. Even though we know when boats arrived, the boats are  already gone  when the crabs hatch! The earlier hatching doesn't help boats catch them.

Why C Works:

C gives us  both  critical pieces:
- When boats  LEAVE  (the end of their presence)
- When crabs  HATCH

This directly answers:  "Are the boats still there when the crabs hatch?"

If crabs hatch in October and boats leave in November → Overlap exists → Argument supported
If crabs hatch in November and boats leave in October → No overlap → Argument fails

Answer: C

In the last few years, a drastic spike in sea temperatures around Prud

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In the last few years, a drastic spike in sea temperatures around Prud

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