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Behavioral psychologists apprehend that conditioned fear responses to atone previously paired with a shock diminish, if the tone is repeatedly presented without the shock, a process known as extinction. Since Parlor it has been hypothesized that this extinction does not erase conditioning, but forms a new memory. Research has now demonstrated that destruction of the infralimbic cortice blocks recall of fear extinction, indicating that it might store long-term extinction memory. Infralimbic neurons recorded during fear conditioning and extinction fire to the tone only when rats are recalling extinction on the following day, and rats indicating the least fear responses also demonstrate the greatest increase in infralimbic tone responses. Conditioned tones paired with brief electrical stimulation of infralimbic cortex elicit low fear responses in rats that have not undergone extinction. Thus, stimulation resembling extinction-induced infralimbic tone responses is able to simulate extinction memory. Which of the following most accurately describes the passage（）
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The average population density of the world is 47 persons per square mile. Continental densities range from no permanent inhabitants in Antarctica to 211 per square mile in Europe. In the western hemisphere, population densities range from about 4 per square mile in Canada to 675 per square mile in Puerto Rico. In Europe the range is from 4 per square mile in Iceland to 831 per square mile in the Netherlands. Within countries there are wide variations of population densities. For example, in Egypt, the average is 55 persons per square mile, but 1,300 persons inhabit each square mile in settled portions where the land is arable. High population densities generally occur in regions of developed industrialization, such as the Netherlands, Belgium, and Great Britain, or where lands are intensively used for agriculture, as in Puerto Rico and Java. Low average population densities are characteristic of most underdeveloped countries. Low density of population is generally associated with a relatively low percentage of cultivated land. This generally results from poor-quality lands. It may also be due to natural obstacles to cultivation, such as deserts, mountains or malaria-infested jungles, to land uses other than cultivation, as pasture and forested land, to primitive methods that limit cultivation, to social obstacles, and to land ownership systems which keep land out of production. More economically advanced countries of low population density have, as a rule, large proportions of their populations living in urban areas. Their rural population densities are usually very low. Poorer developed countries of correspondingly low general population density, on the other hand, often have a concentration of rural population living on arable land, which is as great as the rural concentration found in the most densely populated industrial countries. Along the banks of the Nile, we may expect to find ______.
Why does the Foundation concentrate its support on basic rather than applied research Basic research is the very heart of science, and its cumulative product is the capital of scientific progress, a capital that must be constantly increased as the demands upon it rise. The goal of basic research is understanding, for its own sake. Understanding of the structure of the atom or the nerve cell, the explosion of a spiral nebula or the distribution of cosmic dust, the causes of earthquakes and droughts, or of man as a behaving creature and of the social forces that are created whenever two or more human beings come into contact with one another--the scope is staggering, but the commitment to truth is the same. If the commitment were to a particular result, conflicting evidence might be overlooked or, with the best will in the world, simply not appreciated. Moreover, the practical applications of basic research frequently cannot be anticipated. When Roentgen, the physicist, discovered X-rays, he had no idea of their usefulness to medicine. Applied research, undertaken to solve specific practical problems, has an immediate attractiveness because the results can be seen and enjoyed. For practical reasons, the sums spent on applied research in any country always far exceed those for basic research, and the proportions are more unequal in the less developed countries. Leaving aside the funds devoted to research by industry--which is naturally far more concerned with applied aspects because these increase profits quickly--the funds the U.S. Government allots to basic research currently amount to about 7 percent of its overall research and development funds. Unless adequate safeguards are provided, applied research invariably tends to drive out basic. Then, as Dr. Waterman has pointed out, "Developments will inevitably be undertaken prematurely, career incentives will gravitate strongly toward applied science, and the opportunities for making major scientific discoveries will be lost. Unfortunately, pressures to emphasize new developments, without corresponding emphasis upon pure science tend to degrade the quality of the nation’s technology in the long run, rather than to improve it.\ The title below that best expresses the ideas of this passage is ______.
预期通货膨胀提高时，无风险利率会随着提高，进而导致证券市场线的向上平移。风险厌恶感的加强，会提高证券市场线的斜率。 ( )
公司持有有价证券的年利率为6%，公司的现金最低持有量2 500元，现金余额的最优返回线为9 000元，如果公司现有现金21 200元，则根据随机模型应将其中的8BO元投资于证券。 ( )
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