1. The typological theory of species classification, which has few adherents today, distinguishes species solely on the basis of observable physical characteristics, such as plumage color, adult size, or dental structure. However, there are many so-called “sibling species,” which are indistinguishable on the basis of their appearance but cannot interbreed and thus, according to the mainstream biological theory of species classification, are separate species. Since the typological theory does not count sibling species as separate species, it is unacceptable.
The reasoning in the argument is most vulnerable to criticism on the grounds that

2. Deirdre: Many philosophers have argued that the goal of every individual is to achieve happiness—that is, the satisfaction derived from fully living up to one’s potential. They have also claimed that happiness is elusive and can be achieved only after years of sustained effort. But these philosophers have been unduly pessimistic, since they have clearly exaggerated the difficulty of being happy. Simply walking along the seashore on a sunny afternoon causes many people to experience feelings of happiness.
Which one of the following most accurately describes a reasoning flaw in Deirdre’s argument?

3. It would not be surprising to discover that the trade routes between China and the West were opened many centuries, even millennia, earlier than 200 B.C., contrary to what is currently believed. After all, what made the Great Silk Road so attractive as a trade route linking China and the West—level terrain, easily traversable mountain passes, and desert oases—would also have made it an attractive route for the original emigrants to China from Africa and the Middle East, and this early migration began at least one million years ago.
That a migration from Africa and the Middle East to China occurred at least one million years ago figures in the above reasoning in which one of the following ways?

4. Landscape architect: If the screen between these two areas is to be a hedge, that hedge must be of either hemlocks or Leyland cypress trees. However, Leyland cypress trees cannot be grown this far north. So if the screen is to be a hedge, it will be a hemlock hedge.
In which one of the following is the pattern of reasoning most similar to that in the landscape architect’s argument?

5. We can now dismiss the widely held suspicion that sugar consumption often exacerbates hyperactivity in children with attention deficit disorder. A scientific study of the effects of three common sugars—sucrose, fructose, and glucose—on children who have attention deficit disorder, with experimental groups each receiving a type of sugar in their diets and a control group receiving a sugar substitute instead of sugar, showed no statistically significant difference between the groups in thinking or behavior.
Which one of the following, if true, would most weaken the argument above?

6. Chiu: The belief that a person is always morally blameworthy for feeling certain emotions, such as unjustifiable anger, jealousy, or resentment, is misguided. Individuals are responsible for only what is under their control, and whether one feels such an emotion is not always under one’s control.
Chiu’s conclusion follows logically if which one of the following is assumed?

7. Columnist: A recent research report suggests that by exercising vigorously, one significantly lowers one’s chances of developing certain cardio-respiratory illnesses. But exercise has this effect, the report concludes, only if the exercise is vigorous. Thus, one should not heed older studies purporting to show that nonstrenuous walking yields the same benefits.
The reasoning in the columnist’s argument is most vulnerable to criticism on the grounds that this argument

8. We already knew from thorough investigation that immediately prior to the accident, either the driver of the first vehicle changed lanes without signaling or the driver of the second vehicle was driving with excessive speed. Either of these actions would make a driver liable for the resulting accident. But further evidence has proved that the first vehicle’s turn signal was not on, though the driver of that vehicle admits to having changed lanes. So the driver of the second vehicle is not liable for the accident.
Which one of the following would be most important to know in evaluating the conclusion drawn above?

9. It is a mistake to think, as ecologists once did, that natural selection will eventually result in organisms that will be perfectly adapted to their environments. After all, perfect adaptation of an individual to its environment is impossible, for an individual’s environment can vary tremendously; no single set of attributes could possibly prepare an organism to cope with all the conditions that it could face.
Which one of the following most accurately expresses the main conclusion of the argument?

10. Global ecological problems reduce to the problem of balancing supply and demand. Supply is strictly confined by the earth’s limitations. Demand, however, is essentially unlimited, as there are no limits on the potential demands made by humans. The natural tendency for there to be an imbalance between demand and sustainable supply is the source of these global problems. Therefore, any solutions require reducing current human demand.
Which one of the following is an assumption on which the argument depends?

11. In a poll of a representative sample of a province’s residents, the provincial capital was the city most often selected as the best place to live in that province. Since the capital is also the largest of that province’s many cities, the poll shows that most residents of that province generally prefer life in large cities to life in small cities.
The argument is most vulnerable to the criticism that it

12. Economist: Contrary to the usual assumption, an increase in average family income is not always a sign of economic improvement. For example, in one country, an increase in the average family income coincided with a substantial increase in unemployment. What happened was that many low-income workers lost their jobs, leaving a smaller number of higher-paid workers, thereby increasing the average family income. Thus, increases in average family income should not necessarily be taken as evidence of economic improvement.
The economist’s conclusion follows logically if which one of the following is assumed?

13. Philosopher: An action is morally good if it both achieves the agent’s intended goal and benefits someone other than the agent.
Which one of the following judgments most closely conforms to the principle cited by the philosopher?

14. Geneticist: Genes, like viruses, have a strong tendency to self-replicate; this has led some biologists to call genes “selfish.” This term is, in this instance, intended to be defined behaviorally: it describes what genes do without ascribing intentions to them. But even given that genes are ascribed no intentions, the label “selfish” as applied to genes is a misnomer. Selfishness only concerns bringing about the best conditions for oneself; creating replicas of oneself is not selfish.
Which one of the following, if assumed, allows the geneticist’s conclusion to be properly drawn?

15. Critic: Although filmmakers frequently profess an intention to produce original work, such claims are belied by the widespread use of generic conventions that predetermine the structures of most films. Plot structures, character types, and even themes and visual motifs, all based on formulas long popular with both filmmakers and audiences, are still in general use. To what extent can a filmmaker’s work be considered original if it follows such predetermined formulas?
Which one of the following is a principle underlying the critic’s argument?

16. Some statisticians believe that the method called extreme value theory (EVT) is a powerful analytical tool. The curves generated by traditional statistical methods to analyze empirical data on human longevity predict that some humans would live beyond 130 years. According to the curves EVT generates, however, the limit on human life spans is probably between 113 and 124 years. To date, no one has lived beyond the upper limits indicated by EVT analysis.
Which one of the following can be properly inferred from the statements above?

17. Editorial: Almost every year the Smithfield River floods the coastal fishing community of Redhook, which annually spends $3 million on the cleanup.

Some residents have proposed damming the river, which would cost $5 million but would prevent the flooding. However, their position is misguided.

A dam would prevent nutrients in the river from flowing into the ocean. Fish that now feed on those nutrients would start feeding elsewhere. The loss of these fish would cost Redhook $10 million annually.
Which one of the following most accurately expresses the main conclusion of the editorial’s argument?

18. Psychologist: Most people have some conscious awareness of their motivations for their actions, but the influence of motives of which people are unaware is often much stronger. This has been demonstrated by social science research showing that the subconscious motives people offer as their reasons for their behavior often differ from the reasons offered by independent observers.
Which one of the following conclusions is best supported by the psychologist’s statements?

19. The number of different synthetic chemical compounds that are known to be carcinogenic but are nonetheless used as pesticides, preservatives, or food additives is tiny compared to the number of nonsynthetic carcinogenic compounds widely found in plants and animals. It is therefore absurd to suppose that the rise in the cancer rate in recent decades is due to synthetic carcinogens. The reasoning above is most vulnerable to criticism on the grounds that it overlooks the possibility that

20. Advertisement: Seventy-five percent of dermatologists surveyed prefer Dermactin to all other brands of skin cream. Why? We consulted dermatologists during the development of Dermactin to ensure that you have the best skin cream on the market. So if you need a skin cream, use Dermactin.
The reasoning in the advertisement is questionable because the advertisement

21. Industrial adviser: If two new processes under consideration are not substantially different in cost, then the less environmentally damaging process should be chosen. If, however, a company already employs an environmentally damaging process and retooling for a less damaging process would involve substantial cost, then that company should retool only if retooling is either legally required or likely to bring long-term savings substantially greater than the cost.
Which one of the following judgments conforms most closely to the principles described by the industrial adviser?

22. Editor: Newspapers tend to become more profitable when they increase their circulations, but they must balance this against maintaining journalistic integrity. For example, a profitable tabloid’s success is often based on sensationalist stories that are only loosely tied to actual events, while a respected newspaper’s success is often based on its reputation for being a trustworthy source. Thus, a newspaper that loses sight of its purpose in order to increase circulation is unlikely to achieve long-term profitability.
Which one of the following can be properly inferred from the editor’s argument?