1. The presence of microorganisms that produce a toxin cause sweater to turn brownish red, phenomenon known as a red ride. Sea otters do not feed in areas where clams, their main source of food, have become contaminated with this toxin. According to a proposed explanation of the otter’s behavior, the otters sample the clams in a potential feeding area and can taste any toxin in them.
Which of the following, if true, would most strongly indicate that the hypothesis described in the last sentence of the passage is not correct?
(A) In some of the area where red tides occur, neither clams nor sea otters are indigenous species.
(B) The presence of sea otters in a given area has a significant effect on which other marine organisms are to be found in that areas.
(C) When seawater in an area unaffected by red tide is artificially dyed brownish red, sea otters do not feed on the clams in that area.
(D) If the clams in a given areas are contaminated with toxin, sea otters move to other areas in search of food.
(E) Although very small amounts of the toxin produced during a red tide are not harmful, large doses can be fatal to animals the size of sea otters.
2. Since 1945 there have been numerous international confrontations as tense as those that precipitated the Second World War, and yet no large-scale conflict has resulted. To explain this, some argue that fear of enormous destruction such as the Second War produced has had a dramatic deterrent effect.
Which of the following, if true, most seriously weakens the deterrent theory mentioned above?
(A) After the First World War, the fear of great future destruction was as intense as it was after the Second World War.
(B) Psychologists have determined that the fear of retaliation tends to temper aggressiveness among human beings.
(C) The Second World War was far less distractive than most people generally believe.
(D) Fear of repeating the levels of destruction that the Second World War produced is as pervasive today as it was forty years ago.
(E) Many of the international confrontations that have occurred since 1945 have involved countries that participated in the Second World War.
3. A conservation group in the United States is trying to change the long-standing image of bats as frightening creatures. The group contends that bats are feared and persecuted solely because they are shy animals that are active only at night.
Which of the following, if true, would cast the most serious doubt on the accuracy of the group’s contention?
A. Bats are steadily losing natural roosting places such as caves and hollow trees and are thus turning to more developed areas for roosting.
B. Bats are the chief consumers of nocturnal insects and thus can help make their hunting territory more pleasant for humans.
C. Bats are regarded as frightening creatures not only in the United States but also in Europe, Africa, and South America.
D. Raccoons and owls are shy and active only at night; yet they are not generally feared and persecuted.
E. People know more about the behavior of other greatly feared animal species, such as lions, alligators, and greatly feared animal species, such as lions, alligators, and snakes, than they do about the behavior of bats.
4.(Z13)Healthy lungs produce a natural antibiotic that protects them from infection by routinely killing harmful bacteria on airway surfaces. People with cystic fibroses, however, are unable to fight off such bacteria, even though their lungs produce normal amounts of the antibiotic. Since the fluid on airway surfaces in the lungs of people with cystic fibrosis bas an abnormally high salt concentration, scientists hypothesize that in high salt environments the antibiotic becomes ineffective at killing harmful bacteria.
Which of the following, if it were obtained as an experimental result, would most decisively undermine the scientists’ hypothesis?
A. Healthy lungs in which the salt concentration of the airway-surface fluid has been substantially increased are able to reestablish their normal salt concentration within a relatively short period of time.
B. The antibiotic produced by the lungs is effective at killing harmful bacteria even when salt concentrations are below levels typical of healthy lungs.
C. The salt concentration of the airway-surface fluid in the lungs of people who suffer from cystic fibrosis tends to return to its former high levels after having been reduced to levels typical of healthy lungs.
D. The lungs of people who suffer from cystic fibrosis are unable to fight off harmful bacteria even when the salt concentration is reduced to levels typical of healthy lungs.
E. The salt concentration in the airway-surface fluid of people whose lungs produce lower-than-average amounts of the antibiotic is generally much lower than that typical of healthy lungs.
5. The number of people diagnosed as having a certain intestinal disease has dropped significantly in a rural county this year, as compared to last year. Health officials attribute this decrease entirely to improved sanitary conditions at water-treatment plants, which made for cleaner water this year and thus reduced the incidence of the disease.
Which of the following, if true, would most seriously weaken the health officials' explanation for the lower incidence of the disease?
(A) Many new water-treatment plants have been built in the last five years in the rural county.
(B) Bottled spring water has not been consumed in significantly different quantities by people diagnosed as having the intestinal disease, as compared to people who did not contract the disease.
(C) Because of a new diagnostic technique, many people who until this year would have been diagnosed as having the intestinal disease are now correctly diagnosed as suffering from intestinal ulcers.
(D) Because of medical advances this year, far fewer people who contract the intestinal disease will develop severe cases of the disease.
(E) The water in the rural county was brought up to the sanitary standards of the water in neighboring counties 10 years ago.
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