【正文】 time intervals(tens to hundreds of years), species ranges rarely expand thousands of miles or across physical barriers such as oceans or mountains. Habitat modification can create conditions favorable to the establishment of nonindigenous species. Soil disturbed in construction and agriculture is open for colonization by nonindigenous weeds, which in turn may provide habitats for the nonindigenous insects that evolved with them. Humangenerated changes in fire frequency, grazing intensity, as well as soil stability and nutrient levels similarly facilitate the spread and establishment of nonindigenous plants. When human changes to natural environments span large geographical areas, they effectively create passages for species movement between previously isolated locales. The rapid spread of the Russian wheat aphid to fifteen states in just two years following its 1986 arrival has been attributed in part to the prevalence of alternative host plants that are available when wheat is not. Many of these are nonindigenous grasses remended for planting on the forty million or more acres enrolled in the . Department of Agriculture Conservation Reserve Program. A number of factors perplex quantitative evaluation of the relative importance of various entry pathways. Time lags often occur between establishment of nonindigenous species and their detection, and tracing the pathway for a longestablished species is difficult. Experts estimate that nonindigenous weeds are usually detected only after having been in the country for thirty years or having spread to at least ten thousand acres. In addition, federal port inspection, although a major source of information on nonindigenous species pathways, especially for agriculture pests, provides data only when such species enter via closelyexamined routes. Finally, some parisons between pathways defy quantitative analysis— for example, which is more “important” ： the entry path of one very harmful species or one by which many but less harmful species enter the country? 此資料來(lái)自企業(yè) of the following statements about species movement is best supported by the text? ［ A］ Human factors affect species movement rates more than its longterm amount. ［ B］ Natural expansions of species account for their slow natural contractions. ［ C］ Natural environments created by human activities contribute much to species movement. ［ D］ Longrange movement of species depends on the geographic extent of human mobility. 37According to the text, the . Department of Agriculture ［ A］ contributed to the fast distribution of the Russian wheat aphid to broad areas. ［ B］ failed to isolate the Russian wheat aphid in limited locales. ［ C］ provides data about foreign species entering the country by regulated routes. ［ D］ is responsible for introducing harmful plants onto federal lands. can be inferred that all of the following affect the movement of species EXCEPT ［ A］ earth fertility. ［ B］ import restrictions. ［ C］ natural obstacles. ［ D］ fire disasters. determine the entry pathway for a nonnative species is LEAST likely to depend on ［ A］ whether the species is considered to be a pest. ［ B］ whether the species enters by a closelychecked route. ［ C］ the rate at which the species extends geographically. 此資料來(lái)自企業(yè) ［ D］ the magnitude of the average number of the species. 40Which of the following may best express the chief purpose of the last paragraph? ［ A］ To explain the difficulties in tracing the pathways for longestablished species. ［ B］ To describe the events usually leading to the detection of a nonindigenous species. ［ C］ To identify the problems in assessing the weight of entry tracks for foreignies. ［ D］ To discuss the role of time lags and geographic expansion of species in species detection. Part B Directions: In the following article, some sentences have been removed. For Questions 41— 45, choose the most suitable one from the list A— G to fit into each of the numbered blank. There are two extra choices, which do not fit in any of the gaps. Mark your answers on ANSWER SHEET 1.(10 points) If you fail to stoke a fire,its flames at some time will the great fire of the Sun has burned nonstop for about 5000 million years with no apparent sign of going ).__ People in many cultures regarded the Sun as a miraculous gift from the gods,quite different from earthly fires and therefore not likely to fail them unless the gods were made now know that the Sun will eventually burn ).__ The Sun is posed of almost 75 per cent hydrogen and 25 per cent helium,plus much smaller amounts of oxygen,carbon,neon,nitrogen,magnesium,iron and is known as a main sequence star,one that shines by burning ).__ Thus, the Sun is both burning fuel and creating it. As the hydrogen store diminishes,its stock of helium light and heat ing now from the Sun were actually produced in its core many millions of years ago. 此資料來(lái)自企業(yè) When we burn fuel on a fire,we are converting matter— wood or coal— partly into more efficient the fire,the more heat it ).__This loss of hydrogen is slight when pared to the Suns enormous though i