Practice GMAT Critical Reasoning Question

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Most scientists believe that the decay of the ozone layer is a cause of global warming. With a weaker ozone layer, additional wavelengths of light reach the earth. However, the danger posed by ozone decay is not limited to global warming. The decay of the ozone layer, which enables more harmful wavelengths of light to reach the earth's surface, is also believed to cause permanent eye damage in some animals.

Which of the following is most strongly supported by the statements above?

A)	All wavelengths of light from the sun that damage the eyes of animals are blocked by a healthy ozone layer.
B)	Some animals do not experience damage to their eyes when exposed to unfiltered waves of light.
C)	Only a handful of animal species live in places where they are exposed to the damaging light waves.
D)	The rising temperature of the earth poses a severe threat to animals.
E)	Some wavelengths of light that engender eye damage in certain animals are more likely to hit the earth due to ozone decay.

Correct Answer: E

Due to the question being asked, the correct answer must follow closely from the statements in the stimulus. An answer that intuitively appears correct yet fails to follow closely from the statements in the stimulus is incorrect.

This answer snags a significant number of test takers. However, it is wrong because it draws too broad of a conclusion. The stimulus never indicates that "all" wavelengths that damage the eyes of animals are blocked by a healthy ozone layer. Further, notice the words "which enables more." The word "more" seems to indicate that a healthy ozone enables some wavelengths to pass through.
The fact that the decay in the ozone layer is believed to cause permanent eye damage in some animals does not mean other animals do not experience damage. Similarly, a decay of the ozone layer does not mean that wavelengths are entirely unfiltered. It simply means that less filtering of light exists.
The location of the animals that are damaged is never discussed and has no relevancy on the issue at hand.
Although this statement is true, it is not the main (or even a main) point of the argument. Similarly, the word "severe" is too strong and not supported by the statements in the stimulus.
This statement captures the main argument from the stimulus. Further, it is a near rephrase of "which enables some harmful wavelengths of light to reach the earth's surface."

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