Amphibian populations are declining in numbers worldwide. Not coincide

OFFICIAL EXPLANATION

This question is very difficult than the previous question, in part because one of the wrong answer choices is very attractive.

The conclusion of the argument is a causal statement that the depletion of the ozone layer is the primary cause of the declining amphibian population:



This conclusion is based on the fact that the ozone layer blocks harmful UV-B radiation, which amphibians are vulnerable to in both adult and egg form.

Although the argument mentions UV-B radiation, which may sound impressive, the structure of the reasoning is easy to follow and no knowledge of the radiation is needed. The conclusion is clearly stated and easy to spot due to the indicator “thus.” The question stem is a Strengthen and therefore the four incorrect answers will each strengthen the argument. As with the previous question, look for answers that fit the five causal strengthening answer types discussed earlier.

Answer choice (A): This is the correct answer. The answer fails to shed any light—positive or negative—on the connection between the ozone depletion and the amphibian population decline. Because the argument is concerned with the damage done by UV-B radiation, the fact that UV-B is the only damaging type of radiation blocked by ozone is irrelevant.

Answer choice (B): This answer choice strengthens the argument by showing that when the cause is absent in nonamphibian populations, the effect does not occur (Type C).

Answer choice (C): This answer strengthens the argument by showing that the areas of ozone depletion and amphibian decline match each other, thereby affirming the data used to make the conclusion (Type E).

Answer choice (D): This was the answer most frequently chosen by test takers. This answer choice strengthens the argument by eliminating an alternate cause for the effect (Type A). Had the natural habitat become smaller over the years (from say, human encroachment or climatic change) then that shrinkage would have offered an alternate explanation for the decline in the amphibian population. By eliminating the possibility of habitat shrinkage, the stated cause in the argument is strengthened.

Answer choice (E): This answer strengthens the argument by showing that the decline of the amphibians has mirrored the decline of the ozone layer, thereby affirming the data used to make the conclusion (Type E).

we have to strengthen it...

lets see the choices..
(A) Of the various types of radiation blocked by atmospheric ozone, UV-B is the only type that can damage genes.
We already know that UV-B can damage genes.. NOTHING NEW to strengthen..
Had it said :-
1) the amphibians have been found to have suffered from damaged genes.
2) ONLY UV-B is capable of damaging genes...Here it is just not speaking of rays being blocked but it makes UV-B the only possibility
SO A strong contender unless we find a worse choice

(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.
This gives us reason to believe that UV-B is responsible-- a sureshot strengthener

(C) Atmospheric ozone has been significantly depleted above all the areas of the world in which amphibian populations are declining.
Here again, it is correlating decline to ozone deplition--surely a strengthener

(D) The natural habitat of amphibians has not become smaller over the past century.
For a moment, one can be inclined to it.. But, this eliminates a possibility/ reason for this decline-- so in a way strengthens by removing a contender for the decline

(E) Amphibian populations have declined continuously for the last 50 years.
relating the period of decline with the period of ozone deplition, it strengthens the conclusion..

Only A seems to be doing nothing, apart from repeating something which is already known..

Hope it helps..

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 V-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.

However i am in the list of selecting the wrong option (D) after shortisting A & D. Now when i gave it some more thought D automatically left from my mind leaving only option A to select.
If natural habitat hasn't become smaller that means, for 50 years they were living in the same habitat and no man made or other environmental factors have affected their habitat. That means, if their population have declined, then it might be the reason of UV rays exposure so however slightly this option is strengthening the fact mentioned in the argument.

But if we see the option A, it is just mentioning that UV-B is the one type of radiation that affects genes, with no mention that it is causing decline in amphibian population. It might be that amphibians are getting exposed to UV-B & it is affecting some changes in genes that might or might not resulting in casualties. Hence A is the most apt one.