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During the nineteenth and twentieth centuries, migrations have taken place within__1__ countries; the cities with their industries have attracted people away from the country. The possibility of earning a fixed__2__in a factory or office was more attractive than the possibility of staying on the farm and having ones work __3 __by frost, storms, or droughts. Furthermore, the development of agricultural machinery made it possible for fewer people to do the same __4__of work. Thus, at the same time when the industrial revolution made it possible to produce goods more__5__and more quickly in factories, agricultural revolution also took place. Instead of leaving fields empty every third year, farmers began to plant clover or some other crop that would__6__the soil. Instead of using only animal fertilizer, farmers began to use chemical fertilizers to keep the soil rich. These methods have enabled French farmers, for example, to get five times as much wheat as was __7__ from the same land two centuries ago. In many countries farmers find it more __8__to raise only one crop or one kind of animal. They choose the kind that gives the best results. Then they sell all that they produce, instead of trying to grow a little of everything and consume what they grow. This is a more feasible type of __9__because modern methods and machinery are adapted to specific animals and specific crops. Therefore, it would be too expensive to do all the work by hand, or to buy the__10__needed for several different kinds of farming. | 
