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7.(Z)The Earth’s rivers constantly carry dissolved salts into its oceans.  Clearly, therefore, by taking the resulting increase in salt levels in the oceans over the past hundred years and then determining how many centuries of such increases it would have taken the oceans to reach current salt levels from a hypothetical initial salt-free state, the maximum age of the Earth’s oceans can be accurately estimated.

Which of the following is an assumption on which the argument depends?

A.        The quantities of dissolved salts deposited by rivers in the Earth’s oceans have not been unusually large during the past hundred years.
B.        At any given time, all the Earth’s rivers have about the same salt levels.
C.        There are salts that leach into the Earth’s oceans directly from the ocean floor.
D.        There is no method superior to that based on salt levels for estimating the maximum age of the Earth’s oceans.
E.        None of the salts carried into the Earth’s oceans by rivers are used up by biological activity in the oceans.

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8.(Z)Most household appliances use electricity only when in use. Many microwave ovens, however, have built-in clocks and so use some electricity even when they are not in use. The clocks each consume about 45 kilowatt-hours per year. Therefore, house holds whose microwave oven has no built-in clock use 45 kilowatt-hours per year less, on average, than do comparable households shoes microwave oven is other-
wise similar but has a built-in clock.

Which of the following is an assumption on which the argument depends?
A.        Households that do not have a microwave oven use less energy per year, on average, than do households that have a microwave oven.
B.        Microwave ovens with a built-in clock do not generally cost more to buy than microwave ovens without a built-in clock.
C.        All households that have a microwave oven also have either a gas oven or a Conventional electric oven.
D.        Households whose microwave oven does not have a built-in clock are no more likely to have a separate electric clock plugged in than households whose microwave oven has one.
E.        There are more households that have a microwave oven with a built-in clock than there are households that have a microwave oven without a built-in clock.

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9(Z). The milk of many mammals contains cannabinoids, substances that are known to stimulate certain receptors in the brain. To investigate the function of cannabinoids, researchers injected newborn mice with a chemical that is known to block cannabinoides from reaching their receptors in the brain. The injected mice showed far less interest in feeding than normal newborn mice do. Therefore, cannabinoids probably function to stimulate the appetite.

Which of the following is an assumption on which the argument depends?
A.        Newborn mice do not normally ingest any substance other than their
mothers’ milk.
B.        Cannabinoids are the only substances in mammals’ milk that stimulate the appetite.
C.        The mothers of newborn mice do not normally make any effort to encourage their babies to feed.
D.        The milk of mammals would be less nutritious if it did not contain cannabinoids.
E.        The chemical that blocks cannabinoids from stimulating their brain receptors does not independently inhibit the appetite.

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10.(Z)Frobisher, a sixteenth-century English explorer, had soil samples from Canada’s Kodlunarn Island examined for gold content.  Because high gold content was reported, Elizabeth I funded two mining expeditions.  Neither expedition found any gold there.  Modern analysis of the island’s soil indicates a very low gold content.  Thus the methods used to determine the gold content of Frobisher’s samples must have been inaccurate.

Which of the following is an assumption on which the argument depends?

A.        The gold content of the soil on Kodlunarn Island is much lower today than it was in the sixteenth century.
B.        The two mining expeditions funded by Elizabeth I did not mine the same part of Kodlunarn Island.
C.        The methods used to assess gold content of the soil samples provided by Frobisher were different from those generally used in the sixteenth century.
D.        Frobisher did not have soil samples from any other Canadian island examined for gold content.
E.        Gold was not added to the soil samples collected by Frobisher before the samples were examined.

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11.(Z)In Kravonia, the average salary for jobs requiring a college degree has always been higher than the average salary for jobs that do not require a degree. Current enrollments in Kravonia’s colleges indicate that over the next four years the percentage of the Kravonian workforce with college degree will increase dramatically. Therefore, the average salary for all workers in Kravonia is likely to increase over the next four years.

Which of the following is an assumption on which the argument depends?
A.        Kravonians with more than one college degree earn more, on average, than do Kravonians with only one college degree.
B.        The percentage of Kravonians who attend college in order to earn higher salaries is higher now than it was several years ago.
C.        The higher average salary for jobs requiring a college degree is not due largely to a scarcity among the Kravonian workforce of people with a college degree.
D.        The average salary in Kravonia for jobs that do not require a college degree will not increase over the next four years.
E.        Few members of the Kravonian workforce earned their degrees in other countries.

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12(Z).In the years following an eight-cent increase in the federal tax on a pack of cigarettes, sales of cigarettes fell ten percent. In contrast, in the year prior to the tax increase, sales had fallen one percent. The volume of cigarette sales is therefore strongly related to the after-tax price of a pack of cigarettes.

The argument above requires which of the following assumptions?

A.        During the year following the tax increase, the pretax price of a pack of cigarettes did not increase by as much as it had during the year prior to the tax increase.
B.        The one percent fall in cigarette sales in the year prior to tax increases was due to a smaller tax increase.
C.        The pretax price of a pack of cigarettes gradually decreased throughout the year before and the year after the tax increase.
D.        For the year following the tax increase, the pretax price of a pack of cigarettes was not eight or more cents lower than it had been the previous year.
E.        As the after-tax price of a pack of cigarettes rises, the pretax price also rises.

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13.(Z)In 1992 outlaw fishing boats began illegally harvesting lobsters from the territorial waters of the country of Belukia. Soon after, the annual tonnage of lobster legally harvested in Belukian waters began declining; in 1996, despite there being no reduction in the level of legal lobster fishing activity, the local catch was 9,000 tons below pre-1992 levels. It is therefore highly likely that the outlaw fishing boats harvested about 9,000 tons of lobster illegally that year.

Which of the following is an assumption on which the argument depends?

A.        The illegal lobster harvesting was not so extensive that the population of catchable lobsters in Belukia’s territorial waters had sharply declined by 1996
B.        The average annual lobster catch, in tons, of an outlaw fishing boat is has increased steadily since 1992.
C.        Outlaw fishing boats do not , as a group, harvest more lobsters than do licensed lobster-fishing boats.
D.        The annual legal lobster harvest in Belukia in 1996 was not significantly less than 9,000 tons.
E.        A significant proportion of Belukia’s operators of licensed lobster-fishing boats were out of business between 1992 and 1996

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14.(Z)For most people, the left half of the brain controls linguistic capabilities, but some people have their language centers in the right half. When a language center of the brains is damaged, for example, by a stroke, linguistic capabilities are impaired in some way. Therefore, people who have suffered a serious stroke on the left side of the brain without suffering any such impairment must have their language centers in the right half.

Which of the following is an assumption on which the reasoning in the argument above depends?

A.        No part of a person’s brain that is damaged by a stroke never recovers
B.        Impairment of linguistic capabilities does not occur in people who have not suffered any damage to any language center of the brain.
C.        Strokes tend to impair linguistic capabilities more severely than does any other cause of damage to language centers in the brain.
D.        If there are language centers on the left side of the brain, any serious stroke affecting that side of the brain damages at least one of them.
E.        It is impossible to determine which side of the brain contains a person’s language centers if the person has not suffered damage to either side of the brain.

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15.(Z)Press Secretary:  Our critics claim that the President’s recent highway project cancellations demonstrate a vindictive desire to punish legislative districts controlled by opposition parties.  They offer as evidence the fact that 90 percent of the projects canceled were in such districts.  But all of the canceled projects had been identified as wasteful in a report written by respected nonpartisan auditors.  So the President’s choice was clearly motivated by sound budgetary policy, not partisan politics.

Which of the following is an assumption on which the press secretary’s argument depends?

A.        Canceling highway projects was not the only way for the President to punish legislative districts controlled by opposition parties.
B.        The scheduled highway projects identified as wasteful in the report were not mostly projects in districts controlled by the President’s party.
C.        The number of projects canceled was a significant proportion of all the highway projects that were to be undertaken by the government in the near future.
D.        The highway projects canceled in districts controlled by the President’s party were not generally more expensive than the projects canceled in districts controlled by opposition parties.
E.        Reports by nonpartisan auditors are not generally regarded by the opposition parties as a source of objective assessments of government projects.

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16.(Z) In a study conducted in Pennsylvania, servers in various restaurants wrote “Thank you” on randomly selected bills before presenting the bills to their customers.  Tips on these bills were an average of three percentage points higher than tips on bills without the message.  Therefore, if servers in Pennsylvania regularly wrote “Thank you” on restaurant bills, their average income from tips would be significantly higher than it otherwise would have been.

Which of the following is an assumption on which the argument relies?

A.        The “Thank you” messages would have the same impact on regular patrons of a restaurant as they would on occasional patrons of the same restaurant.
B.        Regularly seeing “Thank you” written on their bills would not lead restaurant patrons to revert to their earlier tipping habits.
C.        The written “Thank you” reminds restaurant patrons that tips constitute a significant part of the income of many food servers.
D.        The rate at which people tip food servers in Pennsylvania does not vary with how expensive a restaurant is.
E.        Virtually all patrons of the Pennsylvania restaurants in the study who were given a bill with “Thank you” written on it left a larger tip than they otherwise would have.