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

The dusky salamander lives only in slow-moving streams where organic debris settles and accumulates. In almost all places in New York State where dusky salamanders used to live, suburban development has cleared uplands and put down asphalt. As a result, rainwater now runs directly into streams, causing increased flow that slows the accumulation of organic sediments. 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.

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

  1. Since 1980 the suburban population of New York State has grown ten times faster than its urban population.
  2. 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.
  3. 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.
  4. Suburban development in New York State contributes significantly to pollution of local streams with lawn fertilizers that are poisonous to most small aquatic animals.
  5. Much of the suburban development in New York State has been occurring in areas that never provided prime habitat for dusky salamanders.

An important thing to keep in mind about the Reading Comprehension section of the GRE as we use PowerPrep online to study is that it is just that—reading comprehension. In other words, as difficult as it may seem, and it can be pretty tricky, the test makers will always give us all the information we need in the passage to answer the question. Questions that ask us to strengthen or weaken an argument, like question 18 of the second Verbal section on practice test 1, may have answer choices not found in the passage, but we should keep in mind that the information we need is still there.

This question specifically asks about an “argument.” When a GRE question asks about an argument there are a few key structural ideas that we should keep in mind: the premises, conclusion, and any assumptions. The premises are the facts or pieces of evidence an argument is based on. The conclusion is the position that the argument is meant to support, and assumptions are any details that were not part of the premises but that would have to be true in order for the conclusion to be true.

Specifically, this question wants us to find an example that strengthens the support of the argument, so we’ll want to search for an answer that bolsters the conclusion, or something that could be added to the argument as another premise for the conclusion. It is nearly impossible to predict what this something could be, so we want to do our best to be very familiar with the given premise(s) and conclusion of the argument so that we’ll be better equipped to recognize what might add information that contributes in a positive way.

The argument discusses a particular species of salamander that only lives in a particular environment, slow-moving streams. In nearly all of its habitats in New York State, development has occurred, meaning more asphalt (so far so good, all of this sounds like it’s building to something). Our next sentence begins “as a result,” which could fake us out—we might think that this next sentence will give us the conclusion, but it actually just states another fact that is the result of this previous fact. Apparently, the additional asphalt has an effect on the speed of streams because rainwater runs directly into them. The final sentence begins with “therefore,” which is often a signal that we’ve reached the conclusion of the argument (as is the fact that this sentence qualifies itself by saying it is “probably” the case). Apparently suburban development is responsible to the dusky salamander’s endangerment in New York State because it has increased the flow of the streams.

Ok so, we should note the parts of this argument:

Conclusion: Increased flow caused by suburban development is responsible for the “virtual disappearance” of the dusky salamander from NY state.

Premises:

  1. Suburban development means more asphalt
  2. More asphalt means rainwater goes directly into streams making them faster
  3. Fast-moving streams are not a good environment for the dusky salamander, which lives in slow-moving streams where sediment can settle

Again, we cannot really predict an exact answer for this question unless we’re amazingly prescient. What we CAN predict is what a good answer will look like. A good answer might illustrate how there was not another factor that could have contributed to the salamander’s disappearance. Let’s see if any of our answers offer this.

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

This answer may seem to support the overall idea that suburban development has had an impact on the environment at large, but it doesn’t really further support this specific conclusion that suburban development is responsible for this particular salamander. In other words, the passage already told us that nearly all of the environments in which the salamander lives have been affected by suburban development, so adding information about the extent of this type of development will not really help. Also, the arbitrary year 1980 is just meant to make this answer sound good, but doesn’t connect at all with the passage and should be a red flag. We can eliminate A.

  • 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.

Again this answer talks about development, which we already know has occurred in almost all of the salamander’s environments. Just because the haven’t been developed in decades does not mean that these areas haven’t seen suburban development at some time in the past. Additionally, we’re not given a timeline for the salamanders disappearance; it could have happened when these areas were developed. We can eliminate B.

  • 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 answer talks about another type of salamander that is not as particular about its habitat. Apparently, this salamander’s population has not been affected. If this salamander has continued to thrive, that seems to suggest that there is not some other factor (such as maybe pollution) that would kill salamanders in streams of New York State. This answer could help bolster the conclusion by providing an example of a similar species that was able to survive the change in the movement of the streams. We should keep C, but it seems like it isn’t necessarily the BEST support to ever exist—it does sort of assume that there aren’t other differences between the two types of salamander. Let’s check the other answers to see if one provides stronger support.

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

This is definitely strong support for the idea that suburban development is responsible for the decline in the dusky salamander population—except, was our conclusion simply that suburban development caused their decline? Nope. The last sentence of the paragraph, which provides our conclusion, specifically said that “increased clow caused by suburban development” was responsible. This answer would actually weaken the argument, then, by providing an alternative reason why the salamanders may have disappeared that also happens to be connected to suburban development. We should eliminate D.

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

This answer doesn’t actually provide us with relevant information. It could be true, but the passage told us that almost all of the habitats where these salamanders lived were affected by suburban development, so even if the majority of suburban development didn’t happen near these streams, the majority of these streams were affected by this development. We can eliminate E.

Indeed, C is the only answer that provides any kind of support for our conclusion. Since we know that the two-lined salamander CAN survive in a swift-moving water system, it makes sense that these salamanders would still thrive even if dusky salamanders declined. C is the best answer.

 

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