In a polluted area around the Great Lakes, scientists

D for me. But It took me close 2.5 minutes. I believe that "Scientists have concluded that the herring gulls have a higher survival rate because they are able to find alternative sources of food" points to the answer. Scientist concluded that gulls are able to find alternative sources of food. and the option D substantiates that.

In a polluted area around the Great Lakes, scientists studying bird populations have observed a drop in the number of both herring gulls and terns. Both bird species prey on the same type of fish, whose numbers are also being negatively affected by pollution. However, the tern population has seen a much sharper decrease than the herring gull population. Scientists have concluded that the herring gulls have a higher survival rate because they are able to find alternative sources of food, including garbage dumps along the shoreline.

Which of the following, if true, would provide the best piece of evidence in support of the researchers' conclusion?


A) A survey shows that bird populations in areas around the Great Lakes have shown similar decreases.
B)A related study finds that fish populations in the Great Lakes are affected as much by other predators as by pollution.
C) Maps of the area reveal that the largest garbage dump in the area is located 3 miles inland from the lake.
D) Blood tests performed on the gulls reveal high levels of the types of fatty acids generally found only in human food.
E)Analysis of water in the area where the birds nest reveals that toxin levels are actually slightly below fish tolerance levels.

Why 'D' and Why not 'C' ?

This question requires a piece of evidence to support scientist's conclusion - Herring gulls have a higher survival rate because they are able to find alternative sources of food. The evidence can be in any applicable form which proves Gulls have actually ate something from alternative source of food, e.g. a scientific test on Gulls or people sighting a flock of gulls sitting on garbage dumps eating leftovers.

A) A survey shows that bird populations in areas around the Great Lakes have shown similar decreases.
-- outside of scope
B)A related study finds that fish populations in the Great Lakes are affected as much by other predators as by pollution.
-- Irrelevant for conclusion
C) Maps of the area reveal that the largest garbage dump in the area is located 3 miles inland from the lake.
-- It does not support the conclusion. Stating the presence of garbage dump near lake does not prove whether gulls are feeding from the garbage as their alternative source. Hence this choice is incorrect due to lack of evidence.
D) Blood tests performed on the gulls reveal high levels of the types of fatty acids generally found only in human food.
-- Correct! These tests reveal that Gull's blood contains the fatty acids generally found ONLY in human food, hence those gulls must be feeding from garbage dumps or other source of human foods.
E)Analysis of water in the area where the birds nest reveals that toxin levels are actually slightly below fish tolerance levels.
-- This does not provide any evidence to support the conclusion.

Hi Aristocrat,

Compare the two choices which are two contenders for strengthening the conclusion

C) Maps of the area reveal that the largest garbage dump in the area is located 3 miles inland from the lake.

Map is a hard evidence that says the largest garbage dump in the area is located 3 miles inland from the lake. which indirectly refutes the premise that herring gulls have a higher survival rate because they are able to find alternative sources of food, including garbage dumps along the shoreline.

And as premise is taken by its words, we cannot the refute the same.


whereas

D) Blood tests performed on the gulls reveal high levels of the types of fatty acids generally found only in human food.

Strengthens the arg. conlcusion that the birds are getting their food from the waste irrespective of what the source of the food is.


Pls let me know if i'm missing a pt here.

Thanks

How can we claim that
garbage dump contains mostly of food waste consumed by human.

How 'C' refutes an argument.
it may be supporting that because of close proximity of garbage dump.
birds might be feeding on them.

My explanation above mentions "garbage dumps or other source of human foods", since the evidence from gull's blood test proves the presence of fatty acids generally found only in human food.

The main argument does not limit its claim to Garbage dumps as the only source. It states "they are able to find alternative sources of food, including garbage dumps along the shoreline". That means Gulls might be also feeding from other alternative sources of food. Hence our objective to show evidence that Gulls are feeding from alternate source of food (other than their primary source fish), whether its garbage dumps or alternate sources such as human food.

Hi Aristocrat,

I'll focus here on the main pt of the argument.Pls let me know if i'm incorrect here.

Premise : Because they (gulls) are able to find alternative sources of food, including garbage dumps along the shoreline.

Conclusion : Scientists have concluded that the herring gulls have a higher survival rate

Assumption: Food found from alternative source/garbage dump is consumable by birds leading to higher survival rate.

Hence D strengthens the arg. saying that "Blood tests performed on the gulls reveal high levels of the types of fatty acids generally found only in human food."


As per my understanding considering the factor of location is out of scope here.

Also C says that garbage dump is 3 miles inside.

As it involves assuming that whether the distance of 3 miles is near or farther. Hence it could be refuting/strengthening the argument depending upon the assumption under consideration.

Thanks
Jatin

In a polluted area around the Great Lakes, scientists studying bird populations have observed a drop in the number of both herring gulls and terns. Both bird species prey on the same type of fish, whose numbers are also being negatively affected by pollution. However, the tern population has seen a much sharper decrease than the herring gull population. Scientists have concluded that the herring gulls have a higher survival rate because they are able to find alternative sources of food, including garbage dumps along the shoreline.

Which of the following, if true, would provide the best piece of evidence in support of the researchers’ conclusion?

A) A survey shows that bird populations in areas around the Great Lakes have shown similar decreases.
B) A related study finds that fish populations in the Great Lakes are affected as much by other predators as by pollution.
C) Maps of the area reveal that the largest garbage dump in the area is located 3 miles inland from the lake.
D) Blood tests performed on the gulls reveal high levels of the types of fatty acids generally found only in human food.
D) Analysis of water in the area where the birds nest reveals that toxin levels are actually slightly below fish tolerance levels.

Hi Zarrolou , May I get your opinion on this one ? Why is "C" Not correct ? the passage clearly talks about Garbage Bump "....higher survival rate because they are able to find alternative sources of food, including garbage dumps along the shoreline".

We have to prove that "herring gulls have a higher survival rate because they are able to find alternative sources of food (garbage dumps)".

For sure C and D are close. But there is one difference that you should consider

C) Maps of the area reveal that the largest garbage dump in the area is located 3 miles inland from the lake.
D) Blood tests performed on the gulls reveal high levels of the types of fatty acids generally found only in human food.

C says that there are dumps in the area and nothing else: this does not mean that the herring gulls eat garbage.
D says that herring gulls have eaten human foods, and this supports the conclusion that they eat from alternative sources of food.

Hope that what I mean is clear

Exactly.

One more thing, IMO C actually attacks the conclusion because it says that the garbage is located 3 miles inland from the shoreline, which contradicts the scientist's conclusion, that the garbage IS along the shoreline.

I have selected D but I agree that D is not perfect choice but better than C

C)Maps of the area reveal that the largest garbage dump in the area is located 3 miles inland from the lake.
Yes Hull birds could travel far in search of food and they could be eating food from garbage and is very possible for struggle for existence

D) Blood tests performed on the gulls reveal high levels of the types of fatty acids generally found only in human food.
If food is readily available in seashore than travelling far for 3 miles to get garbage food. Also this shows that may be humans are readily feeding birds with their food that. Means more content of human food which is considered garbage in terms of bird is available large in sea-shores.

So D is better than C but not a perfect answer. Hope it helped.

I was confused between C and D. C can be eliminated on the fact that presence of Garbage dump doesn't mean that gulls are eating from it. But I am also not convinced that D is an answer as, nothing in the choice indicates that presence of fatty acid similar to humans, indicate gulls are eating from garbage dumps

Option D confirms that the gulls have an alternative source of nutrition. Therefore it supports the scientists' conclusion that "the herring gulls have a higher survival rate because they are able to find alternative sources of food". The part "including garbage dumps along the shoreline" need not be used for selecting option D (though the assumption that garbage dump contains human food is not illogical.)

[Moreover this is a strengthening type question, and hence the "must be true" condition need not be satisfied.]

D shows a causal relation that supports the conclusion.
Any tips to read question, detect negative words, and interpret stem fast and accurate?

I choose C, how can it be assume that garbage contains only human food waste.

from- nkmungila

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