Critical Reasoning

During the month of May, crabs arrive in Delware's beaches to lay eggs. Certain shorebirds depend on these eggs for food during their annual spring migration to their northern breeding grounds. Delware's crab population has declined recently. This decline, however, poses no serious threat to the migrating shorebird populations: by remaining longer in Delware, the birds will be able to eat enough crabs eggs to allow them to complete their migration.

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

A: No other food available to the birds on Delware's beaches is as nutritious and accessible as are the crab eggs
B: The decline in the number of crabs on Delware's beaches is due to te harvesting of crabs by humans
C: There are more crabs on Delware's beaches than in any other area that the migrating birds pass through
D: The crabs do not conceal their eggs
E: The earlier in the season the shorebirds complete their migration, the more likely they are to breed successfully.

Any take on this - esp. if you could dissect the argument- and attack all choices.
Source: GMATPrep Park1


Thanks

During the month of May, crabs arrive on Delaware's beaches to lay eggs. Certain shorebirds depend on these eggs for food during their annual spring migration to their northern breeding grounds. Delaware's crab population has declined recently. This decline, however, poses no serious threat to the migrating shorebird populations: by remaining longer in Delaware, the birds will be able to eat enough crab eggs to allow them to complete their migration.

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

A. No other food available to the birds on Delaware's beaches is as nutritious and accessible as are crab eggs.
B. The decline in the number of crabs on Delaware's beaches is due to the harvesting of crabs by humans.
C. There are more crabs on Delaware's beaches than in any other area that the migrating birds pass through.
D. The crabs do not conceal their eggs.
E. The earlier in the season the shorebirds complete their migration, the more likely they are to breed successfully.

Plan: By remaining longer in Delaware, the birds will be able to eat enough crab eggs to allow them to complete their migration.
Conclusion: The decline in the crab population poses no serious threat to the migrating shorebird populations.

To weaken the conclusion, the correct answer must show that -- even if the birds remain longer in Delaware and eat enough food -- they still face a serious threat.
E: The earlier in the season the shorebirds complete their migration, the more likely they are to breed successfully.
Implication:
By remaining longer in Delaware, the birds are LESS likely to breed successfully, WEAKENING the conclusion that the birds do not face a serious threat.

The correct answer is E.

Thanks GmatGuru.

Analyzing B & D:

Generally, there is a decline in eggs and the result might threaten the shorebitd population.
Cause: Decline in crab eggs; Effect: Threat to the shorebird population.

B: States the cause of the "Cause & Effect" relationship i.e why the decline occurred.
Doesn't effect the mission to breed in the north.

D: The decline in eggs is not because the eggs are concealed;
Here it may seem to say that even if the birds wait any longer, they will not be able to eat
more crab eggs as none is hidden from sight. Until probably the crabs lay more eggs.
So, mission for breeding in the north may be threaten in D; What do u think?

Thanks

GMATGuruNY wrote: By remaining longer in Delaware, the birds are LESS likely to breed successfully, WEAKENING the conclusion that the birds do not face a serious threat.

The correct answer is E.

This options is very convoluted. Can you please add more stuff to simplify this.


I didn't find this option very easy based on prethinking. This is a very convoluted option.
The question stem concludes that even the declining population of crab eggs is not a threat for shorebirds.
They question stem than add a reason (=by remaining longer in Delaware, the birds will be able to eat enough crabs eggs to allow them to complete their migration) to justify the above conclusion.

This question is an example that every time we directly do not try to break the conclusion to weaken the argument, but we have to look the whole argument or the other part(s) of the argument too.

E) The earlier in the season the shorebirds complete their migration, the more likely they are to breed successfully.
OR
This could be alternatively viewed as => the longer they stay the less likely their chances to breed successfully.

gmatdriller wrote:Thanks GmatGuru.

Analyzing B & D:

Generally, there is a decline in eggs and the result might threaten the shorebitd population.
Cause: Decline in crab eggs; Effect: Threat to the shorebird population.

B: States the cause of the "Cause & Effect" relationship i.e why the decline occurred.
Doesn't effect the mission to breed in the north.

B seems to strengthen the PREMISE that the crab population has declined.
A premise is a FACT.
It cannot be strengthened or weakened.
Eliminate any answer choice that attempts to strengthen or weaken a premise.
Eliminate B.

D: The decline in eggs is not because the eggs are concealed;
Here it may seem to say that even if the birds wait any longer, they will not be able to eat
more crab eggs as none is hidden from sight. Until probably the crabs lay more eggs.
So, mission for breeding in the north may be threaten in D; What do u think?

Thanks

In stating that crabs do not conceal their eggs, D implies that the birds will be able to find crab eggs easily, STRENGTHENING the conclusion that the bird population is not threatened by the decline in the crab population.
Since the correct answer choice must WEAKEN the conclusion, eliminate D.

richachampion wrote:

GMATGuruNY wrote: By remaining longer in Delaware, the birds are LESS likely to breed successfully, WEAKENING the conclusion that the birds do not face a serious threat.

The correct answer is E.

This options is very convoluted. Can you please add more stuff to simplify this.


I didn't find this option very easy based on prethinking. This is a very convoluted option.
The question stem concludes that even the declining population of crab eggs is not a threat for shorebirds.
They question stem than add a reason (=by remaining longer in Delaware, the birds will be able to eat enough crabs eggs to allow them to complete their migration) to justify the above conclusion.

This question is an example that every time we directly do not try to break the conclusion to weaken the argument, but we have to look the whole argument or the other part(s) of the argument too.

E) The earlier in the season the shorebirds complete their migration, the more likely they are to breed successfully.
OR
This could be alternatively viewed as => the longer they stay the less likely their chances to breed successfully.

PLAN: By remaining longer in Delaware, the birds will be able to eat enough crab eggs.
CONCLUSION: The bird population does not face a serious threat from the decline in the crab population.

The correct answer choice must show that the bird population DOES face a serious threat.
The OA indicates that threat:
To breed successfully, the birds need to complete their migration EARLY.
Since the decline in the crab population will not ALLOW the birds to complete their migration early, the birds are less likely to breed successfully -- a clear threat to the bird population.

Thanks, Mr. Hunt.