问答

1答疑

[Reading Comprehension]

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文章：

Line         While the most abundant and dominant species
  within a particular ecosystem is often crucial in
  perpetuating the ecosystem, a “keystone” species,
  here defined as one whose effects are much larger
(5) than would be predicted from its abundance, can
  also play a vital role. But because complex species
  interactions may be involved, identifying a keystone
  species by removing the species and observing
  changes in the ecosystem is problematic. It might
(10) seem that certain traits would clearly define a species
  as a keystone species; for example,
  Pisaster ochraceus is often a keystone predator
  because it consumes and suppresses mussel
  populations, which in the absence of this starfish
(15) can be a dominant species. But such predation on a
  dominant or potentially dominant species occurs in
  systems that do as well as in systems that do not
  have species that play keystone roles. Moreover,
  whereas P. ochraceus occupies an unambiguous
(20) keystone role on wave-exposed rocky headlands,
  in more wave-sheltered habitats the impact of
  P. ochraceus predation is weak or nonexistent,
  and at certain sites sand burial is responsible for
  eliminating mussels. Keystone status appears to
(25) depend on context, whether of particular
  geography or of such factors as community
  diversity (for example, a reduction in species
  diversity may thrust more of the remaining species
  into keystone roles) and length of species
(30) interaction (since newly arrived species in particular
  may dramatically affect ecosystems).


题目：

Which of the following hypothetical experiments most clearly exemplifies the method of identifying species’ roles that the author considers problematic?

选项:

A、A population of seals in an Arctic habitat is counted in order to determine whether it is the dominant species in that ecosystem.
B、A species of fish that is a keystone species in one marine ecosystem is introduced into another marine ecosystem to see whether the species will come to occupy a keystone role.
C、In order to determine whether a species of monkey is a keystone species within a particular ecosystem, the monkeys are removed from that ecosystem and the ecosystem is then studied.
D、Different mountain ecosystems are compared to determine how geography affects a particular species’ ability to dominate its ecosystem.
E、In a grassland experiencing a changing climate, patterns of species extinction are traced in order to evaluate the effect of climate changes on keystone species in that grassland.

答案:

C
1答疑

[Critical Reasoning]

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题目：

Only a reduction of 10 percent in the number of scheduled flights using Greentown's airport will allow the delays that are so common there to be avoided. Hevelia airstrip, 40 miles away, would, if upgraded and expanded, be an attractive alternative for fully 20 percent of the passengers using Greentown airport. Nevertheless, experts reject the claim that turning Hevelia into a full-service airport would end the chronic delays at Greentown.

Which of the following, if true, most helps to justify the experts' position?

选项:

A、Turning Hevelia into a full-service airport would require not only substantial construction at the airport itself, but also the construction of new access highways.
B、A second largely undeveloped airstrip close to Greentown airport would be a more attractive alternative than Hevelia for many passengers who now use Greentown.
C、Hevelia airstrip lies in a relatively undeveloped area but would, if it became a full-service airport, be a magnet for commercial and residential development.
D、If an airplane has to wait to land, the extra jet fuel required adds significantly to the airline's costs.
E、Several airlines use Greentown as a regional hub, so that most flights landing at Greentown have many passengers who then take different flights to reach their final destinations.

答案:

E
1答疑

[Problem Solving]

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题目：

If n is a positive integer and the product of all the integers from 1 to n, inclusive, is divisible by 990, what is the least possible value of n ?

选项:

A、8
B、9
C、10
D、11
E、12

答案:

D
1答疑

[Sentence Correction]

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题目：

While some academicians believe that business ethics should be integrated into every business course, others say that students will take ethics seriously only if it would be taught as a separately required course.

选项:

答案:

B
1答疑

[Critical Reasoning]

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文章：

"Life expectancy" is the average age at death of the entire live-born population. In the middle of the nineteenth century, life expectancy in North America was 40 years, whereas now it is nearly 80 years. Thus, in those days, people must have been considered old at an age that we now consider the prime of life

题目：

Which of the following, if true, undermines the argument above?

选项:

A、In the middle of the nineteenth century, the population of North America was significantly smaller than it is todaMost of the gains in life expectancy in the last 150 years have come from reductions in the number of infants who die in their first year of life
B、Many of the people who live to an advanced age today do so only because of medical technology that was unknown in the nineteenth century
C、The proportion of people who die in their seventies is significantly smaller today than is the proportion of people who die in their eighties
D、More people in the middle of the nineteenth century engaged regularly in vigorous physical activity than do so today

答案:

B
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[Sentence Correction]

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题目：

The gyrfalcon, an Arctic bird of prey, has survived a close brush with extinction; its numbers are now five times greater than when the use of DDT was sharply restricted in the early 1970's.

选项:

答案:

A
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[Problem Solving]

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题目：

Jill, who lives in City C, plans to visit 3 different cities, M, L, and S. She plans to visit each city exactly once and return to City C after the 3 visits. She can visit the cities in any order. In how many different orders can she visit the 3 cities?

选项:

A、3
B、6
C、8
D、9
E、12

答案:

B
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[Critical Reasoning]

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题目：

Humans get Lyme disease from infected ticks. Ticks get infected by feeding on animals with Lyme disease, but the ease of transmission from host animal to tick varies. With most species of host animal, transmission of Lyme disease to ticks is extremely rare, but white-footed mice are an exception, readily passing Lyme disease to ticks. And white-footed mouse populations greatly expand, becoming the main food source for ticks, in areas where biodiversity is in decline.

The information in the passage most strongly supports which of the following?

选项:

A、In areas where many humans are infected with Lyme disease, the proportion of ticks infected with Lyme disease is especially high.
B、Very few animals that live in areas where there are no white-footed mice are infected with Lyme disease.
C、Humans are less at risk of contracting Lyme disease in areas where biodiversity is high.
D、Ticks feed on white-footed mice only when other host species are not available to them.
E、The greater the biodiversity of an area, the more likely any given host animal in that area is to pass Lyme disease to ticks.

答案:

C
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[Critical Reasoning]

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题目：

In Kantovia, physicians' income comes from insurance companies, which require physicians to document their decisions in treating patients and to justify deviations from the companies' treatment guidelines. Ten years ago physicians were allowed more discretion. Most physicians believe that the companies' requirements now prevent them from spending enough time with patients. Yet the average amount of time a patient spends with a physician during an office visit has actually increased somewhat over the last ten years.

Which of the following, if true, most helps to resolve the apparent discrepancy between physicians' perceptions and the change in the actual time spent?

选项:

A、Patients are more likely to be in a hurry nowadays and are less willing to wait a long time to see their physician.
B、Physicians today typically have a wider range of options in diagnosis and treatment to consider with the patient before prescribing.
C、Physicians are increasingly likely to work in group practices, sharing the responsibility of night and weekend work.
D、Most patients would rather trust their physicians than their insurance companies to make decisions about their treatment.
E、Since the insurance companies pay physicians a set amount for each office visit, it is to physicians' financial advantage to see as many patients as possible.

答案:

B
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[Problem Solving]

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题目：

A certain quantity is measured on two different scales, the R -scale and the S -scale, that are related linearly.  Measurements on the R -scale of 6 and 24 correspond to measurements on the S -scale of 30 and 60, respectively.  What measurement on the R -scale corresponds to a measurement of 100 on the S -scale?

选项:

A、20
B、36
C、48
D、60
E、84

答案:

C
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1293浏览

[Undefined]

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Art historian: Unlike many artistic traditions that sought to depict plants native to the local area in a seasonally appropriate way (for example, depicting scenes of spring with the plants in the appropriate stages of development for that season), seventeenth-century Dutch artists specializing in flower paintings almost exclusively chose to depict exotic species of flowers from outside the local area. Painting such species was worthwhile primarily because the art-buying public had developed a strong preference for images of the exotic. The great botanical centers of the time gave the artists direct access to such flowers, which the artists would freely combine in a single painting, regardless of whether the combined species occurred together in the wild, and depicted each in full bloom, regardless of whether those species bloomed at the same time in nature.

Statement: The art historian makes the point that the species of flowers these Dutch artists chose to paint were 1 largely because the species were 2 .

Select for 1 and for 2 the options that complete the statement so that it is most strongly supported by the information provided. Make only two selections, one in each column.
我选的CE，和EC有什么区别？怎么选出EC的？
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3662浏览

[Undefined]

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An unusually severe winter occurred in Europe after the continent was blanketed by a blue haze resulting from the eruption of the Laki Volcano in the European republic of Iceland in the summer of 1984.  Thus, it is evident that major eruptions cause the atmosphere to become cooler than it would be otherwise.
Which of the following statements, if true, most seriously weakens the argument above?
C选项为什么就不会有张冠李戴的问题呢，1984和1982的气候情况能一样吗，C里的火山就可以试用于原文的火山吗
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4030浏览

[Undefined]

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The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is increased by 100 percent, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?
为什么这个题一定是相乘不能是相加呢？y=k1A方-k2B （k1,k2大于0 ），也满足题目说的与A方成正比与B成反比啊？但是这道题只有相乘的情况才能选出正确答案
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1339浏览

[Undefined]

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Tiger beetles are such fast runners that they can capture virtually any nonflying insect.  However, when running toward an insect, the beetles intermittently stop, and then, a moment later, resume their attack.  Perhaps they cannot maintain their pace and must pause for a moment's rest; but an alternative hypothesis is that while running tiger beetles are unable to process the resulting rapidly changing visual information, and so quickly go blind and stop.
 
Which of the following, if discovered in experiments using artificially moved prey insects, would support one of the two hypotheses and undermine the other?
答案C是怎么支持一个猜想又削弱另一个猜想的？
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3005浏览

[GWD]

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The author of the passage implies that which of the following is a possible partial explanation for acquisition behavior during the 1970's and 1980's?
请解释这道题为什么不选C或E，除了正确选项B，我认为文中也正确地提到了这两个选项可以解释acquisition behavior during 1970s and 80s
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2081浏览

[OG]

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The primary purpose of the passage is to
为什么选E不选B
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1336浏览

[Undefined]

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Club X has more than 10 but fewer than 40 members. Sometimes the members sit at tables with 3 members at one table and 4 members at each of the other tables, and sometimes they sit at tables with 3 members at one table and 5 members at each of the other tables. If they sit at tables with 6 members at each table except one and fewer than 6 members at that one table, how many members will be at the table that has fewer than 6 members?
提问小梅老师 这道题求讲一下 我没什么思路 带入数字得的是3
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1407浏览

[Undefined]

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A photography dealer ordered 60 Model X cameras to be sold for $250 each, which represents a 20 percent markup over the dealer's initial cost for each camera. Of the cameras ordered, 6 were never sold and were returned to the manufacturer for a refund of 50 percent of the dealer's initial cost. What was the dealer's approximate profit or loss as a percent of the dealer's initial cost for the 60 cameras?
请问小梅老师 这道题讲讲一下 我算的是19% 原来成本是200每个 亏了6个 每个亏100. 最后得不出答案
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332641浏览

[Undefined]

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Analytical!
请问may老师，这题该用什么思路来做？
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339768浏览

[Undefined]

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Analytical!
请问张老师，这道题为什么D不对？我有我觉得second paragraph最后一句话特别指向D
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