Critical Reasoning

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

OA D

Agree with D ...

Becoz, if the blood samples show that gulls have high levels of fatty acids as found in humans ==> gulls have been feeding on garbage dumps...

Aren't we assuming big time here that garbage mentioned in the passage has such kind of human food waste that this herring gulls feed upon?

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

Could this be the better option. If largest garbage dump is 3 mile inside (distance doesn't matter anyways), then maybe these herring gulls thrived upon this dump only..

I was going for either C or D but I went for D because it mentiones "acids found in human food" which obviously gulls fed upon as opposed to C which just mentiones "garbage dump" which could consist of anything and not food which gulls fed upon.

I would side with D as well... the garbage dump being 3 miles away doesn't really offer an answer, since we aren't aware of how far gulls go in order to feed. If blood tests showed that foods that humans eat were in the gulls' systems, then eating from the garbage is strongly inferable.

My answer would be D as the fight is between C and D. C is acutally the same premise mentioned in question so I will not choose it, we should find some thing else that can support the conclusion.

alternative sources of food

(D)

+

I think 3 miles is quite a distance. Hence, it reduces the chances for (C) to be the answer.

hmboy17 wrote:My answer would be D as the fight is between C and D. C is acutally the same premise mentioned in question so I will not choose it, we should find some thing else that can support the conclusion.

This makes sense! Looking for something extra that can strengthen the conclusion besides what's stated in the premise.

I was torn between [spoiler][C][/spoiler] and [spoiler][D][/spoiler], chose [spoiler][C][/spoiler], but your reasoning makes sense.

I will not go for any option in general, but only option D gives some special attribute to gull, so as to distinguish between gull and terns.
Hence [d]

I'm going with D