Questions 4-6

                Erosion of America´s farmland by wind and water has been a problem since settlers first put the prairies and grasslands under the plow in the nineteenth century.  By the 1930s, more than 282 million acres of farmland were damaged by erosion.  After 40 years of conservation efforts, soil erosion has accelerated due to new demands placed on the land by heavy crop production.  In the years ahead, soil erosion and the pollution problems it causes are likely to replace petroleum scarcity as the nation´s most critical natural resource problem.

                4. Land erosion is probably worse in which of the following areas?