A serious threat to farmers in many parts of the world is erosion. Erosion occurs if a large area of land is cleared of trees and is then badly treated by the farmers. The rain and winds may gradually wash away, or blow away, much of the topsoil. When this happens, crops of wheat or corn become weaker and weaker until nothing grows well. If erosion continues, it will turn good land into a desert. In the past, when erosion appeared, farmers sometimes moved to a new place to farm. Sometimes they could not move, but continued to try to grow food in the unhealthy soil. This caused them to sink into poverty. Soon some people realized that there was little rich, fertile soil in the world, government began to try to stop erosion. One of the first experiments to stop erosion began in the prefix = st1 /United Statesin 1933. The experiment was carried out in the area of the Tennessee River. Floods and had farming in this area had ruined land that had once been rich. As a result, most of the people living around the Tennessee River were very poor. The government built big dams across the river and stored the water for use during the dry season when there was no rain. The government workers also helped farmers to fertilize their soil and to learn new farming methods which could stop erosion. At the beginning, the farmers were not interested. But soon,  good healthy crops began to appear on the land where new methods where used. Ten years after the extremely prosperous, the great success of this experiment had led similar projects in the other parts of the world. The passage tells us that erosion is a problem which_.
first began in the United Statesin 1933 occurs mainly in river areas affects many parts of the world is becoming more and more serious
Question: A serious threat to farmers in many parts of the world is erosion. Erosion occurs if a large area of land is cleared of trees and is then badly treated by the farmers. The rain and winds may gradually wash away, or blow away, much of the topsoil. When this happens, crops of wheat or corn become weaker and weaker until nothing grows well. If erosion continues, it will turn good land into a desert. In the past, when erosion appeared, farmers sometimes moved to a new place to farm. Sometimes they could not move, but continued to try to grow food in the unhealthy soil. This caused them to sink into poverty. Soon some people realized that there was little rich, fertile soil in the world, government began to try to stop erosion. One of the first experiments to stop erosion began in the prefix = st1 /United Statesin 1933. The experiment was carried out in the area of the Tennessee River. Floods and had farming in this area had ruined land that had once been rich. As a result, most of the people living around the Tennessee River were very poor. The government built big dams across the river and stored the water for use during the dry season when there was no rain. The government workers also helped farmers to fertilize their soil and to learn new farming methods which could stop erosion. At the beginning, the farmers were not interested. But soon,  good healthy crops began to appear on the land where new methods where used. Ten years after the extremely prosperous, the great success of this experiment had led similar projects in the other parts of the world. The passage tells us that erosion is a problem which_.
A. first began in the United Statesin 1933
B. occurs mainly in river areas
C. affects many parts of the world
D. is becoming more and more serious
Answer: