Complete Question Explanation
Method of Reasoning—Argument Part. The correct answer choice is (D)
The test makers will often reward test takers who have good time-management skills with a relatively
easy question at the end of a section. Hence test takers who are simply marking random answer choices
for the last several questions may forfeit some easy points.
In this stimulus, the toxicologist notes that dioxin causes cancer in rats. Because of this the toxicologist
recommends that the use of dioxin should be banned. Even though dioxin has not been proven harmful
to humans, the fact that it causes cancer in rats is used to justify a complete ban on dioxin. This is best
expressed by answer choice (D).
Answer choice (A): The toxicologist is concerned with preventing cancer in general (particularly in
humans), and that is why he or she advocates a dioxin ban. If the toxicologist were only concerned with
preventing cancer in rats, then the conclusion would simply state, “Because dioxin causes cancer in rats,
rats should not be exposed to dioxin.” But by advocating a complete ban on dioxin in the conclusion, it
is clear that the toxicologist is concerned with more than preventing cancer in rats.
Answer choice (B): This is similar to an Opposite Answer. The toxicologist presents the recent research
on rats exposed to dioxin to illustrate a potential harm of not acting on the conclusion, not to show a
Answer choice (C): The fact that dioxin causes cancer in rats may very explain why similar research will
never be done on humans, but the argument does not use that fact in this manner. The toxicologist is not
trying to prove anything about human research; the toxicologist is trying to prove that the use of dioxin
should be completely banned.
Answer choice (D): This is the correct answer choice. The course of action advocated in the
conclusion is to completely ban the use of dioxin. The toxicologist advocates this ban because dioxin
causes cancer in rats. The inference, of course, is that it may also cause cancer in or be similarly harmful
to humans or other species.
Answer choice (E): Again, the toxicologist is not trying to prove any claims about human research.
In fact, this question type (Method of Reasoning) instructs test takers to accept the claim that similar
research has never been done on humans without having to provide any evidence to that effect. It is true
simply because the toxicologist states that it is true.