This is a correlation - causation type argument. A way of strengthening a causal relationship is to show that there is no third factor that could have resulted in salamander's disappearance. Choice C does the same though not explicitly. By giving an example of a similar species, it shows that no other factor such as disease, pollutants etc could have resulted in salamander's population. Had it been the case then two-line salamander would have decreased in population as well.

Explanation

Passage Paragraph Argument for the GRE is what Critical reasoning stand for on the GMAT. They are the same. As such, the same principles, the same technique to tackle the question might be applied.

The best thing to do is to dissect the argument sentence by sentence and read very super careful. This is a tough one.

The dusky salamander lives only in slow-moving streams where organic debris settles and accumulates.

This is a fact. No doubt on this. This kind of reptile lives in rivers where the water flow is slow. The consequence of this is clearly stated: the debris accumulates and the animal can feed itself.

Do not underestimate the power of this sentence. It is quite clear that this is a key concept to keep in mind. Ask to yourself why the question starts off with such assertion ?? because it plays a pivotal role in the economy as a whole of the entire passage.

In almost all places in New York State where dusky salamanders used to live, suburban development has cleared uplands and put down asphalt.


Almost all the habitats in which the salamanders live the human beings have had a huge impact doing something relevant (asphalt)

As a result, rainwater now runs directly into streams, causing increased flow that slows the accumulation of organic sediments.

The direct consequence of this is that the habitat aforementioned is in vast part altered. when the rain comes down from above the result is that it floes faster than before (due to the asphalt) washing away in most part the sediments. I.E. this perpetual movement of the water does not permit the sediment just to do what they are called for: sediments. Sediments pile up, creating a stratification and here is where the salamanders feed.


Therefore, it is probably the increased flow caused by suburban development that is responsible for the dusky salamander's virtual disappearance from New York State.

This is the conclusion announced by the word therefore. What we explained so far is the main reason why the salamanders almost disappeared from NYS.

Which of the following, if true, most strongly supports the argument?

A) Since 1980 the suburban population of New York State has grown ten times faster than its urban population.

This answer as nothing to do with our main goal: find a reason that confirms all the process pointed out in the stimulus. The comparison between the suburban population and the urban population does not explain anything to us.


B) Dusky salamanders have disappeared in the past ten years from some suburban areas of New York State that were originally developed more than a century ago and that have not experienced significant development for decades.

This is interesting what happened ten years ago and more than this when NYS actually was built. We have no bond between this fact and the fact that salamanders are almost extinct in several areas


C) The two-line salamander, a species that lives in both slow and swift-moving waters, continues to thrive in streams in New York State from which dusky salamanders have disappeared.

This statement says that another kind of salamander (the two-line) is able to survive in a condition on the other extreme of our salamanders. This is the right answer. Considering that this other line survives in water in which the sediments do not pile up reinforce our conclusion that the dusky salamander is NOT able to survive in that habitat configuration. If the two-line salamander is doing fine and can handle fast-moving water. then it is less likely that some other factor other than water speed is the real cause of the dusky salamander disappearance.


D) Suburban development in New York State contributes significantly to pollution of local streams with lawn fertilizers that are poisonous to most small aquatic animals.

The pollution does not help us. We care if the water speed is the cause or not.

E) Much of the suburban development in New York State has been occurring in areas that never provided prime habitat for dusky salamanders.

This answer also does not help us because does not explain us the situation in the areas where dusky salamanders DO live

The correct answer is C

What's the answer to this question?

I picked A



I totally can't see how C would the be answer. Am I missing something here?

Hi,

I have updated my explanation of the entire question and fixed the timer in the question.

Hope this helps now.

Regards

Thank you! I can see why most of them don't fit, but I'll have to spend more time thinking about why choice C is correct. I'm glad the forum has questions that really stretch your mind!

Follow my advice atop and how to dissect the argument: piece by piece.

the most difficult questions will become more manageable.

Regards

This is a thinker and a great one for practice. I could eliminate most choices instantly but was stuck with C and D. When we read carefully, we know C is the answer. The question states what will 'support' this argument.

Thanks for the question!

This is a wonderful example of how process of elimination can aid in answering the question, even if the "right" answer is unclear. As many of us have faced challenges with understanding the relationship between what choice C actually means with respect to the passage, this is the only choice that contains the relevant information without adding extraneous detail that would falsify it: references to different water speed and a parallel to another salamander.

Carcass has done a fine job explaining why the other choices are not suitable.

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