【文章內(nèi)容簡(jiǎn)介】 best supported by paragraph 4?(a)Agricultural development contributed to development in other parts of the economy.(b)European agricultural products were of a higher quality than those produced in the United States.(c)The growing settlement of the West led to a decrease in agricultural production.(d)Farmers were influenced more by government policies than by market opportunities.Question 2129 The wide variety of climates in North America has helped spawn a plex pattern of soil regions. In general, the realm’s soils also reflect the broad environmental partitioning into “humid America” and “arid America.” Where annual precipitation exceeds 20 inches(50 centimeters),soils in humid areas tend to be acidic in chemical content, Since crops (5 ) do best in soils that are neither acidic(higher in acid content) nor alkaline(higher in salt content).fertilization is necessary to achieve the desired level of neutrality between the two. Arid America’s soils are typically alkaline and must be fertilized back toward neutrality by adding acidic pounds. Although many of these dryland soils, particularly in the Great Plains, are quite fertile, European settlers learned over a century ago that (10) water is the main missing ingredient in achieving their agricultural potential. In the 1970’s, certain irrigation methods were perfected and finally provided a real opportunity to expand more intensive farming west from the Central Lowland into the drier portions of the Great Plains. Glaciation also enhanced the rich legacy of fertile soils in the central United States,both from the deposition of mineralrich glacial debris left by meltwater(15) and from thick layers of fine windblown glacial material, called loess, in and around the middle Mississippi Valley. Natural vegetation patterns could be displayed on a map of North America, but the enormous human modification of the North American environment in modern times has all but reduced this regionalization scheme to the level of the hypothetical. Nonetheless,(20) the humid Americaarid America dichotomy is still a valid generalization: the natural vegetation of areas receiving more than 20 inches of water yearly is forest, whereas the drier climates give rise to a grassland cover. The forests of North America tent to make a broad transition by latitude. In the Canadian North, needleleaf forests dominate, but these coniferous trees bee mixed with broadleaf deciduous trees as one crosses the (25) border into the Northeast United States. As one proceeds toward the Southeast, broadleaf vegetation bees dominant. Arid America mostly consists of shortgrass prairies or stepper. The only areas of true desert are in the Southwest.21 What aspect of North America does the passage mainly discuss?(A) The wide variety of climates(B) Soil types and vegetation patterns(C) Improved irrigation methods and the expansion of agriculture(D) The change in precipitation patterns22 The word “spawn ” in line 1 is closest in meaning to (A) distinguish(B) eliminate(C) protect (D) create23 The word “partitioning” in line 2 is closest in meaning to (A) division(B) modification(C) opening(D) circulating24 According to the passage, acidic soils tent to be associated with(A) a high salt content(B) an increase in farming(C) large amounts of rain(D) glacial meltwater25 The word “enhanced” in line 13 is closest in meaning to (A) implied(B) increased(C) indicated(D) informed26 How did glacial meltdown affect the soil in North America?(A) It redistributed the soil types(B) It added salt to the soil(C) It made the soil more neutral in content(D) It added minerals to the soil27 The phrase “this regionalization scheme” in line 19 refers to the (A) movements of glacial deposits(B) patterns of natural vegetation(C) human modification of the North American environment(D) distinction between humid America and arid America28 The word “transition” in line 23 is closest in meaning to (A) elevation(B) change(C) advantage(D) condition29 The passage supports which of the following statements?(A) Arid America is not necessarily characterized by the presence of deserts(B) Most of Canada and the northeastern United States consists of shortgrass prairies wherever natural vegetation has not been modified by humans(C) The accumulation of loes