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  3. In the following article, some sentences have been removed. For Questions 1 — 5, choose the most suitable one from the list A—G

In the following article, some sentences have been removed. For Questions 1 — 5, choose the most suitable one from the list A—G

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问题 In the following article, some sentences have been removed. For Questions 1 — 5, choose the most suitable one from the list A—G to fit into each of the numbered blank. There are two extra choices which you do not need to use.
    Until about two million years ago Africa’s vegetation had always been controlled by the interactions of climate; geology, soil, and groundwater conditions; and the activities of animals. The addition of humans to the latter group, however, has increasingly rendered unreal the concept of a fully developed "natural" vegetation—i. e. , one approximating the ideal of a vegetational climax. 【R1】______. Early attempts at mapping and classifying Africa’s vegetation stressed this relationship: sometimes the names of plant zones were derived directly from climates. In this discussion the idea of zones is retained only in a broad descriptive sense.
    【R2】______. In addition, over time more floral regions of varying shape and size have been recognized. Many schemes have arisen successively, all of which have had to take views on two important aspects; the general scale of treatment to be adopted, and the degree to which human modification is to be comprehended or discounted.
    【R3】______. Quite the opposite assumption is now frequently advanced. An intimate combination of many species—in complex associations and related to localized soils, slopes, and drainage— has been detailed in many studies of the African tropics. In a few square miles there may be a visible succession from swamp with papyrus, the grass of which the ancient Egyptians made paper and from which the word "paper" originated, through swampy grassland and broad-leaved woodland and grass to a patch of forest on richer hillside soil, and finally to juicy fleshy plants on a nearly naked rock summit.
    【R4】______. Correspondingly, classifications have differed greatly in their principles for naming, grouping, and describing formations; some have chosen terms such as forest, woodland, thorn-bush, thicket, and shrub for much of the same broad tracts that others have grouped as wooded savanna(treeless grassy plain)and steppe(grassy plain with few trees). This is best seen in the nomenclature, naming of plants, adopted by two of the most comprehensive and authoritative maps of Africa’s vegetation that have been published; R. W. J. Keay’s Vegetation Map of Africa South of the Tropic of Cancer and its more widely based successor, The Vegetation Map of Africa , compiled by Frank White. In the Keay map the terms "savanna" and "steppe" were adopted as precise definition of formations, based on the herb layer and the coverage of woody vegetation; the White map, however, discarded these two categories as specific classifications. Yet any rapid absence of savanna as in its popular and more general sense is doubtful.
    【R5】______. However, some 100 specific types of vegetation identified on the source map have been compressed into 14 broader classifications.
[A]As more has become known of the many thousands of African plant species and their complex e-cology, naming, classification, and mapping have also become more particular, stressing what was actually present rather than predicting climatic potential.
[B]In regions of higher rainfall, such as eastern Africa, savanna vegetation is maintained by periodic fires. Consuming dry grass at the end of the rainy season, the fires burn back the forest vegetation, check the invasion of trees and shrubs, and stimulate new grass growth.
[C]Once, as with the scientific treatment of African soils, a much greater uniformity was attributed to the vegetation than would have been generally accepted in the same period for treatments of the lands of western Europe or the United States.
[D]The vegetational map of Africa and general vegetation groupings used here follow the White map and its extensive annotations.
[E]African vegetation zones are closely linked to climatic zones, with the same zones occurring both north and south of the equator in broadly similar patterns. As with climatic zones, differences in the amount and seasonal distribution of rainfall constitute the most important influence on the development of vegetatioa
[F]Nevertheless, in broad terms, climate remains the dominant control over vegetation. Zonal belts of rainfall, reflection latitude and contrasting exposure to the Atlantic and Indian oceans and their currents, give some reality to related belts of vegetation.
[G]The span of human occupation in Africa is believed to exceed that of any other continent. All the resultant activities have tended, on balance, to reduce tree cover and increase grassland)but there has been considerable dispute among scholars concerning the natural versus human-caused development of most African grasslands at the regional level.
【R5】
选项
答案D
解析 本题空格出现在第五段段首。下文however一词表明空格部分与下文构成转折关系。下文提到，源图中100种具体的植物类别被缩合为14种涵盖更广的类别。由此可知，空格部分应出现与“图”或“植物类别”有关的内容。符合要求的是[D]，其中the White map与第四段提到的Frank White呼应，its extensive annotations与下文100 specific types呼应。
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