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#10 - The importance of the ozone layer to terrestrial

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Complete Question Explanation

Must be true. The correct answer choice is (E)

Answer choice (A): The very first word—“all”—should be a red flag.
Nowhere in the stimulus do we have support for stating that all damaging
wavelengths are filtered out by the ozone layer. The stimulus only states
that the ozone layer filters “some” wavelengths and lets others through.
Some of those that are filtered are dangerous, as indicated by the last
sentence. Surprisingly, about 10% of all test takers select this answer
choice.

Answer choice (B): We know that many animal species could suffer severe
eye damage, and from this we can infer that some of them live in areas
threatened by holes in the ozone layer. We do not know that few of the
species live in non-threatened areas.

Answer choice (C): Nothing in the passage proves this answer choice. If
you selected this answer thinking that “many” implied “not all,” then you
made a simple, correctable mistake. As we will discuss in the chapter on
Formal Logic, “many” can include “all.”

Answer choice (D): Again, watch those modifiers! One reason the answer
choice is incorrect is because it references “most” species when the
stimulus only discusses “many” species.

Answer choice (E): This is the correct answer. We can follow the chain of
connections in the stimulus to prove this answer: the ozone layer filters
some wavelengths of light; holes in the ozone layer are dangerous, but
one previously overlooked danger of the holes is possible eye damage for
many species. From these two statements we can infer that the holes must
be letting some damaging wavelengths of light through. This is essentially
what answer choice (E) states.
SherryZ
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Hi there, thank you for your generous help!

Dec 2000 LSAT, Sec 3 LR, Q10:

I chose the wrong answer choice C (although I only hesitated between C and E, but bad luck happens all the time).

I thought C is right because in the stimulus, it says "these holes could lead to severe eye damage for animals of MANY species". So, I thought on the other hand, "SOME species of animals have eyes that will not suffer any damage when exposed to unfiltered sunlight" (which is C).

Could you point out my error and explain why C is wrong but E is right??

Thank you very much!

---Sherry
BethRibet
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Hi Sherry,

Thanks for writing!

We can rule out answer choice C because it is not clearly supported by the passage. What we know is that many species will suffer *severe* eye damage, but we have no way to know one way or the other whether there are some who will not suffer *any* damage (which might for instance, include mild damage).

In contrast, answer choice E essentially states an inference that follows logically from the premises stated. That is, if the function of the ozone layer is to filter out some wavelengths of light, and holes pose a danger of severe eye damage, then it would follow that the holes would allow some of the wavelengths that pose that danger to get through.

Hope this clarifies!

Beth
katapult
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Hi Beth,

Could you please explain how to choose between A and E for this problem? I felt they were equally strong and ultimately, but somewhat arbitrarily, picked A. Should I have eliminated A on the basis that something else could prevent the wavelengths that cause eye damage from reaching the earth surface? I thought of it like this:

CanCauseDamageIsFiltered -----> IntactOzone
(X)IntactOzone -----> (X)CanCauseDamageFiltered (where X is Not)

and since the passage confirms the presence of holes, the ozone is not intact, and wavelengths that can cause eye damage are not filtered. Could you please give me feed back on where my reasoning went astray?

Thank you so much for your help!
Francis O'Rourke
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something else could prevent the wavelengths that cause eye damage from reaching the earth surface
That is one possibility that the stimulus does not account for. However there is another possibility that your response leads me to think you are missing. Namely, that there can be wavelengths of light currently reaching Earth’s Surface which can cause eye damage.

The stimulus might lead you to think that all of the dangerous light wavelengths are filtered out, but when you read it closely, it merely states the following:
1. <b>Some</b> wavelengths are completely filtered out
2. Ozone holes could let in wavelengths that lead to severe damage

Notice that the speaker never tell us that every possibly dangerous wavelength is blocked