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Experts suggest that the best way to avoid memory failures is（本题分值：2分）

发布时间：2025-03-26 06:07:51

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答案：B ［A］ to take more ___tary supplements. ［B］ to keep mental function alive. ［C］ to find an in ___ectual oupation. ［D］ to do more in ___ectual exercises. 二、阅读理解题(每题2分，共40分)阅读下列短文，理解意思后选择下列答案中正确的一个Non-indigenous (non-native) species of plants and ani ___ls arrive by way of two general types of pathways. First, species having origins outside the United States ___y enter the country and bee established either as free-living populations or under hu ___n cultivation-for example, in agriculture, horticulture, aquaculture, or as pets. Some cultivated species subsequently escape or are released and also bee established as free-living populations. Second, species of either U.S. or foreign origin and already within the United States ___y spread to new locales. Pathways of both types include intentional as well as unintentional species transfers. Rates of species movement driven by hu ___n transfor ___tions of natural enviro ___ents as well as by hu ___n mobility-through mer ___, touri ___, and travel-greatly ex ___ed natural rates by parison. While geographic distributions of species naturally expand or contract over historical time intervals(tens to hundreds of years), species- ranges rarely expand thousands of miles or across physical barriers such as o ___ans or mountains.Habitat modification can create conditions favorable to the establishment of non-indigenous species. Soil disturbed in construction and agriculture is open for colonization by non-indigenous weeds, which in turn ___y provide habitats for the non-indigenous insects that evolved with them. Hu ___n-generated changes in fire frequency, grazing intensity, as well as soil stability and nutrient levels similarly facilitate the spread and establishment of non-indigenous plants. When hu ___n changes to natural enviro ___ents 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 prevalen ___ of alternative host plants that are available when wheat is not. Many of these are non-indigenous grasses remended for planting on the forty million or more acres enrolled in the U.S. Department of Agriculture Conservation Reserve Program.A number of factors perplex quantitative evaluation of the relative importan ___ of various entry pathways. Time lags often our between establishment of non-indigenous species and their detection, and tracing the pathway for a long-established species is difficult. Experts esti ___te that non-indigenous 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 ___jor sour ___ of infor ___tion on non-indigenous species pathways, especially for agriculture pests, provides data only when such species enter via closely-examined routes. Finally, some parisons between pathways defy quantitative ___ysis-for example, which is more “important”： the entry path of one very harmful species or one by which ___ny but less harmful species enter the country?