Primary Objective #4 and Modifier Words Revisited

In Must Be True questions you are like the detective Sherlock Holmes, looking 
for clues in the stimulus and then matching those clues to the answer choices.
Words like “some,” “could,” and “many” encompass many different possibilities 
and are broad scope indicators. Words like “must” and “none” indicate a
narrow scope.
Primary Objective #4 states: “Read closely and know precisely what the author
said. Do not generalize!” This is especially important in Must Be True questions
because the details are all the test makers have to test you on. Consider the
following stimulus:
2. The importance of the ozone layer to terrestrial
animals is that it entirely filters out some
wavelengths of light but lets others through. Holes in
the ozone layer and the dangers associated with these
holes are well documented. However, one danger that
has not been given sufficient attention is that these
holes could lead to severe eye damage for animals of
many species.
When reading the stimulus, your eye should be drawn to the modifier and
indicator words, which are underlined below:
The importance of the ozone layer to terrestrial
animals is that it entirely filters out some
wavelengths of light but lets others through. Holes in
the ozone layer and the dangers associated with these
holes are well documented. However, one danger that
has not been given sufficient attention is that these
holes could lead to severe eye damage for animals of
many species.
The scope of the stimulus is relatively broad, and aside from the word
“entirely,” most of the modifiers are not absolute.
Now, look at the rest of the problem and see how several of the answer choices
attempt to prey upon those who did not read the stimulus closely. Here are the
question stem and corresponding answer choices for the stimulus above:
2. The importance of the ozone layer to terrestrial
animals is that it entirely filters out some
wavelengths of light but lets others through. Holes in
the ozone layer and the dangers associated with these
holes are well documented. However, one danger that
has not been given sufficient attention is that these
holes could lead to severe eye damage for animals of
many species.
Which one of the following is most strongly
supported by the statements above, if they are true?
(A) All wavelengths of sunlight that can cause eye
damage are filtered out by the ozone layer
where it is intact.
(B) Few species of animals live on a part of the
earth’s surface that is not threatened by holes
in the ozone layer.
(C) Some species of animals have eyes that will not
suffer any damage when exposed to
unfiltered sunlight.
(D) A single wavelength of sunlight can cause
severe damage to the eyes of most species of
animals.
(E) Some wavelengths of sunlight that cause eye
damage are more likely to reach the earth’s
surface where there are holes in the ozone
layer than where there are not.
With the previous discussion in mind, let us analyze the answer choices:
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 the ozone layer. We do not know that few of the species live in nonthreatened
areas. Do not forget the Fact Test—it will eliminate any answer
choice without support.
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.
The lesson from this question is simple: read closely and pay strict attention to
the modifiers used by the author. Even though you must read quickly, the test
makers expect you to know exactly what was said, and they will include
answer choices specifically designed to test whether you understood the details.