1. It is difficult to keep deep wounds free of bacteria. Even strong antibiotics fail to kill the bacteria that live in such wounds. However, many physicians have succeeded in eliminating bacteria from deep wounds by packing the wound with a sweet substance like sugar. Which one of the following, if true, most helps to explain why treating deep wounds with sugar as described above is successful?

2. People who are red/green color-blind cannot distinguish between green and brown. Gerald cannot distinguish between green and brown. Therefore Gerald is red/green color-blind. Which one of the following most closely parallels the reasoning in the argument presented in the passage?

3. Early in this century Alfred Wegener developed the concept of continental drift. His ideas were rejected vehemently because he postulated no identifiable force strong enough to make the continents move. We have come to accept Wegener’s theory, not because we have pinpointed such a force, but because new instruments have finally allowed continental movement to be confirmed by observation. The passage best illustrates which one of the following statements about science?

4. The theory of military deterrence was based on a simple psychological truth, that fear of retaliation makes a would-be aggressor nation hesitate before attacking and is often sufficient to deter it altogether from attacking. Clearly, then, to maintain military deterrence, a nation would have to be believed to have retaliatory power so great that a potential aggressor nation would have reason to think that it could not defend itself against such retaliation. If the statements above are true, which one of the following can be properly inferred?

5. To the Editor: In 1960, an astronomer proposed a mathematical model for determining whether extraterrestrial life exists. It was based on the assumptions that life as we know it could exist only on a planet and that many stars are, like our Sun, orbited by planets. On the basis that there are nine planets in our solar system and one of them has life as we know it, the astronomer predicted that there are as many as one million extraterrestrial civilizations across all solar systems. Yet astronomers to date have not detected even one planet outside our solar system. This indicates that the astronomer’s model is wrong, and life as we know it exists only on the planet Earth. Clay Moltz Which one of the following, if accepted by Clay Moltz, would require him to reconsider his conclusion?

6. If Max were guilty, he would not ask the police to investigate. Therefore, his asking the police to investigate shows that he is not guilty. The logical structure of the argument above is most similar to which one of the following?

7. A population of game ducks at a western lake contains 55 males to every 45 females, while a population of game ducks at an eastern lake contains 65 males for every 35 females. Among those ducks that have not yet bred there are only slightly more males than females, but among older ducks the number of males greatly exceeds the number of females. Because there are appreciably more males among adult ducks than among young ducks, we can infer that the greater the disparity in overall sex ratios, the greater the percentage of older male ducks in the population. Which one of the following can be inferred from the passage?

8. The common procedure for determining whether a food additive should be banned from use is to compare its health-related benefits with its potential risks. Yellow Dye No. 5, an additive used to color lemon soda, might cause allergic reactions in a few consumers. For most consumers of lemon soda, however, the coloring enhances their enjoyment of the beverage. This particular additive should not be banned, therefore, because its benefits greatly outweigh its risks. A flaw in the argument is that the author

9. Fines levied against those responsible for certain environmentally damaging accidents are now so high that it costs a company responsible for such an accident more to pay the fine than it would have cost to adopt measures that would have prevented the accident. Therefore, since businesses value their profits, those that might have such accidents will now install adequate environmental safeguards. Which one of the following, if true, most seriously weakens the argument?

10. Even in a democracy, it is necessary to restrict the dissemination of advanced technological knowledge that is of commercial or national-security value. Dissemination to certain countries, those that are or will be competitors or enemies, should be selectively prohibited. There must, however, be free exchange of scientific information. In order to act in accordance with the position above, it would be necessary to be able to rely on each of the following EXCEPT:

11. Water vapor evaporated from the ocean contains a greater proportion of oxygen-16 and a smaller proportion of the heavier oxygen-18 than does seawater. Normally, this phenomenon has no effect on the overall composition of the ocean, because evaporated seawater returns to the ocean through precipitation. During an ice age, however, a large amount of precipitation falls on ice caps, where it is trapped as ice. Which one of the following conclusions about a typical ice age is most strongly supported by the statements above?

12. Some of the most prosperous nations in the world have experienced a pronounced drop in national savings rates—the percentage of after-tax income an average household saves. This trend will undoubtedly continue if the average age of these nations’ populations continues to rise, since older people have fewer reasons to save than do younger people. Which one of the following indicates an error in the reasoning leading to the prediction above?

13. The term “pit bull” does not designate a breed of dog, as do the terms “German shepherd” and “poodle.” It is like the terms “Seeing-Eye dog” and “police dog,” which designate dogs according to what they do. If you take two German shepherds and place them side by side, you cannot tell by appearance alone which is the police dog and which is the Seeing-Eye dog. Which one of the following is the main point of the passage?

14. Historically, monetary systems have developed only in population centers with marketplaces. Through the fourth century B.C., Mesopotamian cities engaged in trade, but had never had marketplaces. By that period, however, Greek cities all had marketplaces, or agorae. The Greek cities’ agorae were centrally located and goods were traded there either for money or for commodities. If all of the statements in the passage are true, then which one of the following must also be true?

15. Computer operating system software has become increasingly standardized. But when a large business with multiple, linked computer systems uses identical operating system software on all of its computers, a computer vandal who gains access to one computer automatically has access to the data on all the computers. Using a program known as a “virus,” the vandal can then destroy much of the data on all the computers. If such a business introduced minor variations into its operating system software, unauthorized access to all the computers at the same time could be virtually eliminated. Furthermore, variations in operating system software can be created without any loss of computer compatibility to the business. Therefore, it is advisable for businesses to implement such variations. Which one of the following, if true, supports the conclusion in the passage?

16. Computer operating system software has become increasingly standardized. But when a large business with multiple, linked computer systems uses identical operating system software on all of its computers, a computer vandal who gains access to one computer automatically has access to the data on all the computers. Using a program known as a “virus,” the vandal can then destroy much of the data on all the computers. If such a business introduced minor variations into its operating system software, unauthorized access to all the computers at the same time could be virtually eliminated. Furthermore, variations in operating system software can be created without any loss of computer compatibility to the business. Therefore, it is advisable for businesses to implement such variations. Which one of the following can be inferred from the passage?

17. It is the mark of a superior conductor that he or she has the authority to insist, even with a top orchestra, that rehearsal work must be intensified. This authority cannot simply be claimed; the conductor must earn it by winning the orchestra’s respect for the artistic interpretations he or she is currently pursuing. In taking the position outlined, the author presupposes which one of the following?

18. In the United States proven oil reserves—the amount of oil considered extractable from known fields—are at the same level as they were ten years ago. Yet over this same period no new oil fields of any consequence have been discovered, and the annual consumption of domestically produced oil has increased. Which one of the following, if true, best reconciles the discrepancy described above?

19. Train service suffers when a railroad combines commuter and freight service. By dividing its attention between its freight and commuter customers, a railroad serves neither particularly well. Therefore, if a railroad is going to be a successful business, then it must concentrate exclusively on one of these two markets. For the argument to be logically correct, it must make which of the of the following assumptions?

20. Most people in the United States view neither big nor small business as particularly efficient or dynamic and regard both as providing consumers with fairly priced goods and services. However, most people consistently perceive small business as a force for good in society, whereas big business is perceived as socially responsible only in times of prosperity. The statements above, if true, would provide the strongest support for which one of the following hypotheses?

21. The energy an animal must expend to move uphill is proportional to its body weight, whereas the animal’s energy output available to perform this task is proportional to its surface area. This is the reason that small animals, like squirrels, can run up a tree trunk almost as fast as they can move on level ground, whereas large animals tend to slow down when they are moving uphill. Which one of the following is an assumption on which the explanation above depends?

22. The 1980s have been characterized as a period of selfish individualism that threatens the cohesion of society. But this characterization is true of any time. Throughout history all human actions have been motivated by selfishness. When the deeper implications are considered, even the simplest “unselfish” acts prove to be instances of selfish concern for the human species. Which one of the following is a flaw in the argument?

23. A medical journal used a questionnaire survey to determine whether a particular change in its format would increase its readership. Sixty-two percent of those who returned the questionnaire supported that change. On the basis of this outcome, the decision was made to introduce the new format. Which one of the following, if it were determined to be true, would provide the best evidence that the journal’s decision will have the desired effect?

24. Shanna: Owners of any work of art, simply by virtue of ownership, ethically have the right to destroy that artwork if they find it morally or aesthetically distasteful, or if caring for it becomes inconvenient. Jorge: Ownership of unique artworks, unlike ownership of other kinds of objects, carries the moral right to possess but not to destroy. A unique work of art with aesthetic or historical value belongs to posterity and so must be preserved, whatever the personal wishes of its legal owner. Which one of the following principles, if accepted, would contribute most to Shanna’s defense of her position against that of Jorge?

25. Shanna: Owners of any work of art, simply by virtue of ownership, ethically have the right to destroy that artwork if they find it morally or aesthetically distasteful, or if caring for it becomes inconvenient. Jorge: Ownership of unique artworks, unlike ownership of other kinds of objects, carries the moral right to possess but not to destroy. A unique work of art with aesthetic or historical value belongs to posterity and so must be preserved, whatever the personal wishes of its legal owner. On the basis of their statements, Shanna and Jorge are committed to disagreeing about the truth of which one of the following statements?