TOEFL Reading: ETS-TOEFL阅读机经 - 547452R3Q6RY20PML$

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. The 1930s Dust Bowl was a revolutionary event that threatened to destroy United States agriculture by turning the Great Plains into a vast desert. B. The 1930s Dust Bowl in the United States resulted in radical changes in agricultural practices aimed at reducing wind erosion, such as the planting of tree shelterbelts. C. Tree shelterbelts, which are often used in the Great Plains area, are made up of trees that are planted in long rows beside agricultural fields. D. Of all the innovative techniques used to control wind erosion after the 1930s Dust Bowl, only tree shelterbelts proved effective.