Over80percentofmankind’sdietisprovidedbytheseedsofles...

問題詳情：

   Over 80 percent of mankind’s diet is provided by the seeds of less than a dozen plant species. But the amount and variety of crop production has been increasing all the time.

   ____56____For example, Egyptians settled along the River Nile, the Chinese empire along the Yellow River, and the Mesopotamian countries along the Tigris and Euphrates rivers. The river systems provided these early civilizations with a consistent source of silt(泥沙)from the yearly floods and water for the crops.    57  

   Farming changed very little from early times until about 1700. In the 1700s an agricultural revolution took place, which led to a large increase in the production of crops.   58   These crops, such as corn and potatoes, produced very large yields.

   In the 1850s, the industrial revolution came to the farm with new mechanized methods.   59   Early on, the biggest changes were in the use of new farm tools.   60   The new tools, combined with crop rotation(輪作), manure(糞肥)and better soil preparation, led to a steady increase in crop yields in Europe. Later on, the arrival of steam power and, later, gasoline-powered engines represented a big step forward in the production of crops.

A. These methods greatly increased production rates.

B. So people had to work out a new plan to manage the water

C. Many of the early civilizations began along major river systems.

D. Most of the early tools were still powered by horses, oxen or men.

E. Silt is like a natural fertilizer, bringing new minerals to enrich the soil

F. How to increase the crop production has been a problem for human beings

G. One great change in this revolution was the adoption of some different crops

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知識點：七選五題型

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