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5. Since the routine use of antibiotics can give rise to resistant bacteria capable of surviving antibiotic environments, the presence of resistant bacteria in people could be due to the human use of prescription antibiotics. Some scientists, however, believe that most resistant bacteria in people derive from human consumption of bacterially infected meat.

Which of the following statements, if true, would most significantly strengthen the hypothesis of the scientists?

(A) Antibiotics are routinely included in livestock feed so that livestock producers can increase the rate of growth of their animals.
(B) Most people who develop food poisoning from bacterially infected meat are treated with prescription antibiotics.
(C) The incidence of resistant bacteria in people has tended to be much higher in urban areas than in rural areas where meat is of comparable quality.
(D) People who have never taken prescription antibiotics are those least likely to develop resistant bacteria.
(E) Livestock producers claim that resistant bacteria in animals cannot be transmitted to people through infected meat.

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4. In recent years many cabinetmakers have been winning acclaim as artists. But since furniture must be useful, cabinetmakers must exercise their craft with an eye to the practical utility of their product. For this reason, cabinetmaking is not art.

Which of the following is an assumption that supports drawing the conclusion above from the reason given for that conclusion?

(A) Some furniture is made to be placed in museums, where it will not be used by anyone.
(B) Some cabinetmakers are more concerned than others with the practical utility of the products they produce.
(C) Cabinetmakers should be more concerned with the practical utility of their products than they currently are.
(D) An object is not an art object if its maker pays attention to the object’s practical utility.
(E) Artists are not concerned with the monetary value of their products.

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3. Two decades after the Emerald River Dam was built, none of the eight fish species native to the Emerald River was still reproducing adequately in the river below the dam. Since the dam reduced the annual range of water temperature in the river below the dam from 50 degrees to 6 degrees, scientists have hypothesized that sharply rising water temperatures must be involved in signaling the native species to begin the reproductive cycle.

Which of the following statements, if true, would most strengthen the scientists’ hypothesis?

(A) The native fish species were still able to reproduce only in side streams of the river below the dam where the annual temperature range remains approximately 50 degrees.
(B) Before the dam was built, the Emerald River annually overflowed its banks, creating backwaters that were critical breeding areas for the native species of fish.
(C) The lowest recorded temperature of the Emerald River before the dam was built was 34 degrees, whereas the lowest recorded temperature of the river after the dam was built has been 43 degrees.
(D)Nonnative species of fish, introduced into the Emerald River after the dam was built, have begun competing with the declining native fish species for food and space.
(E) Five of the fish species native to the Emerald River are not native to any other river in North America.

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2. Airline: Newly developed collision-avoidance systems, although not fully tested to discover potential malfunctions, must be installed immediately in passenger planes. Their mechanical warnings enable pilots to avoid crashes.

Pilots: Pilots will not fly in planes with collision-avoidance systems that are not fully tested. Malfunctioning systems could mislead pilots, causing crashes.

The pilots’ objection is most strengthened if which of the following is true?
(A) It is always possible for mechanical devices to malfunction.
(B) Jet engines, although not fully tested when first put into use, have achieved exemplary performance and safety records.
(C) Although collision-avoidance systems will enable pilots to avoid some crashes, the likely malfunctions of the not-fully-tested systems will cause even more crashes.
(D) Many airline collisions are caused in part by the exhaustion of overworked pilots.
(E) Collision-avoidance systems, at this stage of development, appear to have worked better in passenger planes than in cargo planes during experimental flights made over a six-month period.

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练习题：
1. The town of Stavanger, Norway, was quiet and peaceful until early 1960’s, when Stavanger became Norway’s center for offshore oil exploration. Between then and now, violent crime and vandalism in Stavanger have greatly increased. Clearly, these social problems are among the results of Stavanger’s oil boom.
  
Which of the following, if it occurred between the early 1960’s and now, gives the strongest support to the argument above?

(A) The people of Stavanger rarely regret that their town was chosen to be Norway’s center for offshore oil exploration.
(B) Norwegian sociologists expressed grave concern about the increase in violent crime and vandalism in Stavanger.
(C) Violent crime and vandalism have remained low in Norwegian that had no oil boom.
(D) Nonviolent crime, drug addiction, and divorce in Stavanger increased approximately as much as violent crime and vandalism did.
(E) The oil boom necessitated the building of wider roads for the increased traffic in Stavanger.

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20.(Z) Lyme disease is caused by a bacterium transmitted to humans by deer ticks. Generally deer ticks pick up the bacterium while in the larval stage from feeding on infected white-footed mice. However, certain other species on which the larvae feed do not harbor the bacterium. Therefore, if the population of these other species were increased, the number of ticks acquiring the bacterium and hence the number of people contracting Lyme disease would likely decline.

Which of the following, if true, most strengthens the argument?

A.        Ticks do not suffer any adverse consequences from carrying the bacterium that causes Lyme disease in humans.
B.        There are no known cases of a human’s contracting Lyme disease through contact with white-footed mice.
C.        A deer tick feeds only once while in the larval stage.
D.        A single host animal can be the source of bacterium for many tick larvae.
E.        None of the other species on which deer tick larvae feed harbor other bacteria that ticks transmit to humans

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19.(Z)In response to viral infection, the immune systems of mice typically produce antibodies that destroy the virus by binding to proteins on its surface.  Mice infected with a herpesvirus generally develop keratitis, a degenerative disease affecting part of the eye.  Since proteins on the surface of cells in this part of the eye closely resemble those on the herpesvirus surface, scientists hypothesize that these cases of keratitis are caused by antibodies to herpesvirus.

Which of the following, if true, gives the greatest additional support to the scientists’ hypothesis?

A.        Other types of virus have surface proteins that closely resemble proteins found in various organs of mice.
B.        There are mice that are unable to form antibodies in response to herpes infections, and these mice contract herpes at roughly the same rate as other mice.
C.        Mice that are infected with a herpesvirus but do not develop keratitis produce as many antibodies as infected mice that do develop keratitis.
D.        There are mice that are unable to form antibodies in response to herpes infections, and these mice survive these infections without ever developing keratitis.
E.        Mice that have never been infected with a herpesvirus can sometimes develop keratitis.

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18.(Z)The traditional treatment of strep infections has been a seven-day course of antibiotics, either penicillin or erythromycin. However, since many patients stop taking those drugs within three days, reinfection is common in cases where these drugs are prescribed. A new antibiotic requires only a three-day course of treatment. Therefore, reinfection will probably be less common in cases where the new antibiotic is prescribed than in cases where either penicillin or erythromycin is prescribed.

Which of the following, if true, most strengthens the argument?
Tricky!!
A.        Some of people who are allergic to penicillin are likely to be allergic to the new antibiotic.
B.        A course of treatment with the new antibiotic costs about the same as a course of treatment with either penicillin or erythromycin.
C.        The new antibiotic has been shown to be effective in eradicating bacterial infections other than strep.
D.        Some physicians have already begun to prescribe the new antibiotic instead of penicillin or erythromycin for the treatment of some strep infections
E.        Regardless of whether they take a traditional antibiotic or the new one, most patients feel fully recovered after taking the drug for three days.

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17.(Z)The Eurasian ruffe, a fish species inadvertently introduced into North America’s Great Lakes in recent years, feeds on the eggs of lake whitefish, a native species, thus threatening the lakes’ natural ecosystem. To help track the ruffe’s spread, government agencies have produced wallet-sized cards about the ruffe. The cards contain pictures of the ruffe and explain the danger they pose; the cards also request anglers to report any ruffe they catch.

Which of the following, if true, would provide most support for the prediction that the agencies’ action will have its intended effect?

A.        The ruffe has spiny fins that make it unattractive as prey.
B.        Ruffe generally feed at night, but most recreational fishing on the Great Lakes is done during daytime hours.
C.        Most people who fish recreationally on the Great Lakes are interested in the preservation of the lake whitefish because it is a highly prized game fish.
D.        The ruffe is one of several nonnative species in the Great Lakes whose existence threatens the survival of lake whitefish populations there.
E.        The bait that most people use when fishing for whitefish on the Great Lakes is not attractive to ruffe.

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16.(Z)A mosquito bite can transmit to a person the parasite that causes malaria, and the use of mosquito nets over children’s beds can significantly reduce the incidence of malarial infection for children in areas where malaria is common. Yet public health officials are reluctant to recommend the use of mosquito nets over children’s beds in such areas.

Which of the following, if true, would provide the strongest grounds for the public health officials’ reluctance?

A.        Early exposure to malaria increases the body’s resistance to it and results in a lesser likelihood of severe life-threatening episodes of malaria.
B.        Mosquito bites can transmit to people diseases other than malaria.
C.        Mosquito nets provide protection from some insect pests other than mosquitoes.
D.        Although there are vaccines available for many childhood diseases, no vaccine has been developed that is effective against malaria.
E.        The pesticides that are most effective against mosquitoes in regions where malaria is common have significant detrimental effects on human health.