Amphibian populations are declining in numbers worldwide. Not coincidentally, the earth’s ozone layer has been continuously depleted throughout the last 50 years. Atmospheric ozone blocks UV-B, a type of ultraviolet radiation that is continuously produced by the sun, and which can damage genes. Because amphibians lack hair, hide, or feathers to shield them, they are particularly vulnerable to UV-B radiation. In addition, their gelatinous eggs lack the protection of leathery or hard shells. Thus, the primary cause of the declining amphibian population is the depletion of the ozone layer.

Each of the following, if true, would strengthen the argument EXCEPT:

(A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes.
(B) Amphibian populations are declining far more rapidly than are the populations of nonamphibian species whose tissues and eggs have more natural protection from
UV-B.
(C) Atmospheric ozone has been significantly depleted above all the areas of the world in
which amphibian populations are declining.
(D) The natural habitat of amphibians has not become smaller over the past century.
(E) Amphibian populations have declined continuously for the last 50 years.

I don't agree with the OE:


Source:CR Powerscore
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IMO the choice is between A and B. others obviously help strengthen the argument.

If we look at B, we'll see B says other animals which are safer from UV-B rays don't have any decline. which, when paraphrased means UV-B rays are the factor behind the decline(which is another way of saying "Because amphibians lack hair, hide, or feathers to shield them, they are particularly vulnerable to UV-B radiation" as stated in the premise). we know "Atmospheric ozone blocks UV-B, a type of ultraviolet radiation that is continuously produced by the sun, and which can damage genes." so if UV-B rays are a factor, then indirectly, the depletion of ozone layer, which allowed the UV-B rays to enter is the cause. So it is STRENGTHENING.

Take A. "Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes" . if this is strengthening the argument then the opposite of this should weaken the argument. what is the opposite?? other type of radiations blocked by atmospheric ozone also cause damage. Now, what is the conclusion of the argument?? "Thus, the primary cause of the declining amphibian population is the depletion of the ozone layer." Is this conclusion weakened in any way by the previous statement?? no. the key here is "blocked by the atmospheric ozone". even if other radiation are the cause of decline, ozone layer depletion will allow those rays to enter and will therefore become an indirect cause. Either way ozone layer depletion is the cause of decline. this does not affect the conclusion. So A is clearly irrelevant, whether it is true or false, doesn't affect the conclusion.

Hence IMO A
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Totally agree with you. Do that during the real exam or a practice CAT. However, during your routine preparation, you have to be sure why you are choosing an option.
That will increase your effectiveness. Otherwise, the chances will decide your score.
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What OE says about D? Why does it strengthen?

D) The natural habitat of amphibians has not become smaller over the past century.