2019年10月27日托福阅读真题+题目+答案：Challenges of Mesopotamian Agriculture

2019年10月27日托福阅读真题+题目+答案：Challenges of Mesopotamian Agriculture

■One of the world's first civilizations began in the area between the Tigris and Euphrates Rivers known as Mesopotamia (modern Iraq), where much of the fertile land was under cultivation by 4500 B.C. ■Sumer, in southern Mesopotamia, was dominated by eight major cities, including the city of Uruk, which had 50,000 inhabitants by 3000 B.C. ■But the irrigation that nourished Mesopotamian fields carried a hidden risk. Groundwater in semiaridcharacterized by low annual rainfall regions usually contains a lot of dissolved salt. ■Where the water table is near the ground surface, as it is in river valleys and deltas, groundwater is moved up into the soil where it evaporates, leaving the salt behind in the ground. When evaporation rates are high, sustained irrigation can generate enough salt to eventually poison crops. While irrigation dramatically increases agricultural output, turning sunbaked floodplains into lush fields can sacrifice long-term crop yields for short-term harvests.

Preventing the buildup of salt in semiarid soils requires either irrigating in moderation or periodically leaving fields fallow (unplanted). In Mesopotamia, centuries of high productivity from irrigated land led to increased population density, which fueled demand for more intensive irrigation. Eventually, enough salt crystallized in the soil that further increases in agricultural production were not enough to feed the growing population.

The key problem for Sumerian agriculture was that the timing of river runoff did not coincide with the growing season for crops. Flow in the Tigris and Euphrates peaked in the spring, when the rivers filled with snowmelt from the mountains to the north. Discharge was lowest in the late summer and early fall, when new crops needed water the most. Intensive agriculture required storing water through soaring summer temperatures. A lot of the water applied to the fields simply evaporated, pushing that much more salt into the soil.。。。。余下托福阅读真题原文省略！

1. According to paragraph 1, all of the following can contribute to the poisoning of crops EXCEPT

A. the repeated use of irrigation

B. farming too close to a group of cities

C. groundwater with high levels of salt

D. water evaporating from the soil at high rates

2. The word "periodically" in the passage is closest in meaning to

A. permanently

B. regularly

C. partially

D. generally

3. According to paragraph 2, how did the rise in population density contribute to the region's agricultural problems?

A. As more of the population settled in cities, there were fewer people to work the fields and maintain the irrigation system.

B. As more land was taken up by houses and other buildings, there was less land available for growing crops.

C. The need to feed a lot of people made it more difficult to cut back on irrigation or let the fields remain unplanted.

D. Waste from the cities added other poisons to the soil in addition to the salt.

。。。。余下托福阅读真题题目省略

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