present a hypothesis
refute an argument
correct a misconception
predict an occurrence
describe an enigma
18. It can be inferred that which of the following is most likely to be the subject of study by a geohydrologist?
Soft, porous rock being worn away by a waterfall
Water depositing minerals on the banks of a gorge through which the water runs
The trapping of water in a sealed underground rock cavern through the action of an earthquake
Water becoming unfit to drink through the release of pollutants into it from a manufacturing plant
The changing course of a river channel as the action of the water wears away the rocks past which the river flows
19. The author refers to many formations primarily in order to
clarify a distinction
introduce a subject
draw an analogy
emphasize a similarity
resolve a conflict
The historian Frederick J. Turner wrote in the 1890s that the agrarian discontent that had been developing steadily in the United States since about 1870 had been precipitated by the closing of the internal frontierthat is, the depletion of available new land needed for further expansion of the American farming system. Not only was Turners thesis influential at the time, it was later adopted and elaborated by other scholars, such as John D. Hicks in The Populist Revolt . Actually, however, new lands were taken up for farming in the United States throughout and beyond the nineteenth century. In the 1890s, when agrarian discontent had become most acute, 1,100,000 new farms were settled, which was 500,000 more than had been settled during the previous decade. After 1890, under the terms of the Homestead Act and its successors, more new land was taken up for farming than had been taken up for this purpose in the United States up until that time. It is true that a high proportion of the newly farmed land was suitable only for grazing and dry farming, but agricultural practices had become sufficiently advanced to make it possible to increase the profitability of farming by utilizing even these relatively barren lands.
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