日期：2008-10-25 Passage 24 All of the cells in a particular plant start out with the same complement of genes. How then can these cells differentiate and form structures as different as roots， stems， leaves， and fruits？ The answer is that only a（5） small subs... 阅读全文>>

日期：2008-10-25 Passage 23 At the end of the nineteenth century， a rising interest in Native American customs and an increasing desire to understand Native American culture prompted ethnolo- gists to begin recording the life stories of Native Amer-（5） ican. Ethn... 阅读全文>>

日期：2008-10-25 Passage 22 Many United States companies have， unfortunately，made the search for legal protection from importcompetition into a major line of work. Since 1980 theUnited States International Trade Commission （ITC）（5） has received about 280 compl... 阅读全文>>

日期：2008-10-25 Passage 21 Bernard Bailyn has recently reinterpreted the earlyhistory of the United States by applying new socialresearch findings on the experiences of Europeanmigrants. In his reinterpretation， migration becomes the（5） organizing principle for... 阅读全文>>

日期：2008-10-25 Passage 20 Species interdependence in nature confers manybenefits on the species involved， but it can also become apoint of weakness when one species involved in the rela-tionship is affected by a catastrophe. Thus， flowering（5） plant species de... 阅读全文>>

日期：2008-10-25 Passage 19 In contrast to traditional analyses of minority busi-ness， the sociological analysis contends that minoritybusiness ownership is a group-level phenomenon， in thatit is largely dependent upon social-group resources for（5） its developme... 阅读全文>>

日期：2008-10-25 Passage 18 Milankovitch proposed in the early twentieth centurythat the ice ages were caused by variations in the Earthsorbit around the Sun. For sometime this theory wasconsidered untestable， largely because there was no suffi-（5） ciently precis... 阅读全文>>

日期：2008-10-25 Passage 17 Prior to 1975， union efforts to organize public-sectorclerical workers， most of whom are women， were some-what limited. The factors favoring unionization drivesseem to have been either the presence of large numbers（5） of workers， as... 阅读全文>>

日期：2008-10-25 Passage 16 In 1896 a Georgia couple suing for damages in theaccidental death of their two year old was told that sincethe child had made no real economic contribution to thefamily， there was no liability for damages. In contrast，（5） less than a... 阅读全文>>

日期：2008-10-25 Passage 15 In the two decades between 1910 and 1930， overten percent to the Black population of the United Statesleft the South， where the preponderance of the Blackpopulation had been located， and migrated to northern（5） states， with the larg... 阅读全文>>

日期：2008-10-25 Passage 14 Nearly a century ago， biologists found that if theyseparated an invertebrate animal embryo into two partsat an early stage of its life， it would survive and developas two normal embryos. This led them to believe that the（5） cells in t... 阅读全文>>

日期：2008-10-25 Passage 13 The majority of successful senior managers do notclosely follow the classical rational model of first clari-fying goals， assessing the problem， formulating options，estimating likelihoods of success， making a decision，（5） and only t... 阅读全文>>

日期：2008-10-25 Passage 12 Federal efforts to aid minority businesses began in the1960s when the Small Business Administration （SBA）began making federally guaranteed loans and govern-ment-sponsored management and technical assistance（5） available to minority bu... 阅读全文>>

日期：2008-10-25 Passage 11 Archaeology as a profession faces two major prob-lems. First， it is the poorest of the poor. Only paltrysums are available for excavating and even less is avail-able for publishing the results and preserving the sites（5） once excavated... 阅读全文>>

日期：2008-10-25 Passage 10 Caffeine， the stimulant in coffee， has been called the most widely used psychoactive substance on Earth . Synder， Daly and Bruns have recently proposed that caffeine affects behavior by countering the activity in（5） the human brain o... 阅读全文>>

日期：2008-10-25 Passage 9 Most economists in the united States seemcaptivated by the spell of the free market. Conse-quently， nothing seems good or normal that doesnot accord with the requirements of the free market.（5） A price that is determined by the seller o... 阅读全文>>

日期：2008-10-25 Passage 8 Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of electromagnetic radiation. Yet there is another form of radiation that permeates the universe：（5） neutrinos. Wi... 阅读全文>>

日期：2008-10-25 Passage 7 Between the eighth and eleventh centuries A.D.， the Byzantine Empire staged an almost unparalleled economic and cultural revival， a recovery that is all the more striking because it followed a long period of severe（5） internal decline.... 阅读全文>>

日期：2008-10-25 Passage 6 In the eighteenth century， Japans feudaloverlords，from the shogun to the humblestsamurai， found themselves under financialstress. In part， this stress can be attributed to（5） the overlords failure to adjust to a rapidly ex-panding ec... 阅读全文>>

日期：2008-10-25 Passage 5 How many really suffer as a result of labor mar-ket problems？ This is one of the most critical yetcontentious social policy questions. In many ways，our social statistics exaggerate the degree of hard-（5） ship. Unemployment does not hav... 阅读全文>>