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As part of a delicately balanced system, the human heart secretes a hormone, a substance that controls the amount of salt in the blood and the volume of blood circulating within the body. Only very small quantities of the hormone are required. This hormone is extremely important in regulating blood pressure and is found in large amounts in the blood of those suffering a heart attack. If the statements above are true, then it must also be true that

A. if there is a deficiency in the amount of heart hormone secreted, low blood pressure will result.
B. it is large quantities of the heart hormone that cause heart attacks to occur.
C. the effects of a small amount of the heart hormone will be long-lasting in the body.
D. if a device that is only a mechanical pump is used as an artificial heart, it will not perform all the functions of the human heart.
E. (E) any drug that regulates blood pressure will have its effect by influencing the amount of the heart hormone secreted.

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Consider three fish swimming together in a school. The space within which each fish can be seen by predator Y is defined by a sphere centered on the fish and having a radius that is the maximum distance Y can see. The school is vulnerable to attack when Y is within one of the three spheres. The spheres overlap to a great extent, since the fish are in a compact group. Which of the following is a reliable inference to be drawn from the passage above

A. The vulnerability to attack of the school as a whole is not much greater than the vulnerability to attack of any one fish in the school.
B. There is less chance that predator Y will attack a school of four fish than that it will attack a school of three fish.
C. Fish who swim in schools are less likely to be devoured by predators than are fish who do not swim in schools.
D. The maximum distance at which an individual fish is visible depends less on the size of the fish than on whether the fish is swimming in a school.
E. (E) The maximum distance at which predator Y can see its prey is increased if Y is itself swimming in a school of Y’s.

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Economist: Any country that is economically efficient will generate wealth. Such a country will remain politically stable only if that wealth is distributed equitably. The equitable distribution of wealth puts an end to risk taking, the indispensable precondition of economic efficiency. Which of the following conclusions can be properly drawn on the basis of the statements above

A. No country can indefinitely remain both economically efficient and politically stable.
B. No country can indefinitely remain both politically unstable and wealthy.
C. Economic efficiency is the indispensable precondition for the generation of wealth in a country.
D. Any country in which wealth is distributed equitably will indefinitely remain politically stable.
E. (E) Growing economic efficiency encourages risk taking, which in turn leads to further growth in economic efficiency.

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To many environmentalists, the extinction of plants—accompanied by the increasing genetic uniformity of species of food crops—is the single most serious environmental problem. Something must be done to prevent the loss of wild food plants or no-longer-cultivated food plants. Otherwise, the lack of genetic diversity could allow a significant portion of a major crop to be destroyed overnight. In 1970, for example, southern leaf blight destroyed approximately 20 percent of the United States corn crop, leaving very few varieties of corn unaffected in the areas over which the disease had spread. Which of the following can be inferred from the passage above

A. Susceptibility to certain plant diseases is genetically determined.
B. Eighty percent of the corn grown in the United States is resistant to southern leaf blight.
C. The extinction of wild food plants can in almost every case be traced to destructive plant diseases.
D. Plant breeders focus on developing plants that are resistant to plant disease.
E. (E) Corn is the only food crop threatened by southern leaf blight.

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In 1987 sinusitis was the most common chronic medical condition in the United States, followed by arthritis and high blood pressure, in that order. The incidence rates for both arthritis and high blood pressure increase with age, but the incidence rate for sinusitis is the same for people of all ages. The average age of the United States population will increase between 1987 and 2000. Which of the following conclusions can be most properly drawn about chronic medical conditions in the United States from the information given above

A. Sinusitis will be more common than either arthritis or high blood pressure in 2000.
B. Arthritis will be the most common chronic medical condition in 2000.
C. The average age of people suffering from sinusitis will increase between 1987 and 2000.
D. Fewer people will suffer from sinusitis in 2000 than suffered from it in 1987.
E. (E) A majority of the population will suffer from at least one of the medical conditions mentioned above by the year 20O0.

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