Spiral galaxies rotate so fast that the gravitational force produced by their visible matter is insufficient to stop them from flying apart. A large amount of invisible or "dark" matter must therefore be holding these galaxies together. Astronomers once believed that this dark matter consisted of massive black holes. However, new calculations show that the gravitational force that would be produced by such black holes would cause stars to "evaporate." Since stars in spiral galaxies are not evaporating in this way, the dark matter holding these galaxies together cannot consist of massive black holes.Which one of the following is a reasoning technique used in the argument above?
Answer(s): A
The argument rejects the hypothesis that dark matter consists of massive black holes because it is inconsistent with what is known to be true--namely, that stars in spiral galaxies are not "evaporating," which would occur if the hypothesis were correct.
Columnist: Awareness of the use of performance enhancing substances by professional athletes threatens to make the use of such potentially dangerous substances socially acceptable among amateur athletes and others. The more we test professional athletes for these substances, the more we will inevitably discover about their drug use. Thus, the goal of preserving professional athletes' status as role models who set a positive example actually seems best served by a policy of no testing.Which one of the following, if true, most strengthens the columnist's argument?
Answer(s): E
The columnist's argument is strengthened by evidence that drug testing has little effect in curtailing professional athletes' use of performance-enhancing substances. This supports the idea that testing might increase public awareness of drug use without actually reducing it, undermining the goal of preserving athletes as positive role models.
Commentator: Lunar research shows that the composition of the Moon is far different from that of Earth. This suggests that two theories about the origin of the Moon are false: the theory that the Moon formed along with Earth and of the same materials; and the theory that the Moon is a large chunk that split off from Earth. Therefore, the Moon was originally a large rock that hit Earth and ricocheted into orbit.The flawed reasoning in which one of the following arguments is most similar to the flawed reasoning in the commentator's argument?
The commentator's reasoning involves dismissing two possibilities (the Moon forming along with Earth or splitting off from Earth) and then concluding that the remaining option (the Moon being a rock that ricocheted into orbit) must be correct without adequately considering other potential explanations. This flawed reasoning mirrors the option, where Jan's rejection of two career options (law and medicine) leads to the unsupported conclusion that Jan must want a career in business, ignoring other possibilities.
Derek: I've discovered a case where a professor published the exact same paper twice, using the same title both times. This is a case of self-plagiarism, and self-plagiarism is an act of academic fraud.Gina: But because the same title was used both times, the professor was not attempting to pass off one piece of work as two. The time to suspect academic fraud is when an author republishes a paper in slightly altered form.Derek's and Gina's positions indicate that they disagree with each other about whether the professor
Answer(s): B
Derek asserts that the professor's actions constitute academic fraud because they represent self-plagiarism.Gina disagrees, arguing that the use of the same title indicates the professor was not attempting to mislead, and thus it does not amount to academic fraud. This shows they disagree about whether the professor engaged in academic fraud.
Environmentalist: During the 1980s, concern for the earth's dwindling forests and the resulting reduction in biodiversity led to efforts to recognize environmentally sustainable and socially responsible timber production by means of timber certification programs. Although such programs fit today's market ethos and are succeeding in economically stable countries, they are not likely to be fully successful in countries that are economically unstable. Thus, in the latter countries, unprecedented and innovative forest preservation efforts must be made.Which one of the following most accurately expresses the conclusion of the environmentalist's argument?
Answer(s): D
The environmentalist concludes that "unprecedented and innovative forest preservation efforts must be made" in economically unstable countries, implying the need for new solutions.
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