Question

    The past 70 years have been good for corn production in the Midwestern United States, with yields increasing fivefold since the 1940s. Much of this improvement has been credited to advances in farming technology but researchers at Harvard University are asking if changes in climate and local temperature may be playing a bigger role than previously thought.

In a newspaper, researchers find that a prolonged(延长的) growing season due to increased temperatures, combined with the natural cooling effects of large fields of plants, have had a major contribution to improved corn production in the U.S. “Our research shows that improvements in crop yields depend, in part, on improvements in climate,” said Peter Huybers, professor of Earth and Planetary Sciences. “In this case, changing temperatures have had a beneficial impact on agricultural production, but there is no guarantee that benefit will last as the climate continues to change.

Understanding the detailed relationships between climate and crop yields is important as we move towards feeding a growing population on a changing planet. ” The researchers modeled the relationship between temperature and crop yields from 1981 to 2017 across the so-called Corn Belt. They found that as temperatures increased due to global climate change, planting days got earlier and earlier, shifting by about three days per decade. Early planting means the corn has more time to mature before the end of the growing season.

There is also a second, more surprising trend that has benefited corn yields. Whereas the vast majority of temperatures have warmed over the last century, the hottest days during the Midwestern growing season have actually cooled.

The researchers estimate that more than one quarter of the increase in crop yields since 1981 can be attributed to the twin effects of a longer growing season and less exposure to high temperatures, suggesting that the crop yield is more vulnerable to climate change than previously thought.

The researchers also show that the planting and harvest dates farmers currently use is significantly better adapted to the present climate than it would be to climates in earlier decades.

1.What is previously thought to be the reason for the increase of corn production?

A.Local temperature change. B.Advanced farming technology.

C.Climate change. D.Production efficiency.

2.Why is it important to understand the relationships between climate and crop yield?

A.The climate has a beneficial impact on agriculture.

B.We can change the climate to improve crop yield.

C.We depend on the climate to get food.

D.Crop yield relies less on the climate.

3.How many factors that benefit corn yields are mentioned in the text?

A.4. B.3.

C.2. D.1.

4.What is the main purpose of the text?

A.To explain a mystery. B.To question a common sense.

C.To show a new trend. D.To introduce a research result.

Answer

1.B

2.C

3.C

4.D

【解析】

这是一篇说明文。文章介绍一项研究结果。在这种情况下，不断变化的气温对农业生产产生了有益的影响，但不能保证这种影响将随着气候的持续变化而持续下去。

1.

推理判断题。根据第一段中Much of this improvement has been credited to advances in farming technology but researchers at Harvard University are asking if changes in climate and local temperature may be playing a bigger role than previously thought.“这种进步很大程度上归功于农业技术的进步，但哈佛大学的研究人员提出了一个问题:气候和当地温度的变化是否在其中发挥了比之前认为的更大的作用?”由此可知，以前认为玉米产量增加的原因是“先进的农业技术。”故选B。

2.

细节理解题。根据第二段中Our research shows that improvements in crop yields depend, in part, on improvements in climate,“我们的研究表明，作物产量的提高在一定程度上取决于气候的改善，”由此可知，之所以理解气候和作物产量之间的关系很重要，是因为我们依靠气候获取食物。故选C。

3.

细节理解题。根据第二段最后一句In this case, changing temperatures have had a beneficial impact on agricultural production, but there is no guarantee that benefit will last as the climate continues to change.“在这种情况下，不断变化的气温对农业生产产生了有益的影响，但不能保证这种影响将随着气候的持续变化而持续下去。”再根据第四段There is also a second, more surprising trend that has benefited corn yields. Whereas the vast majority of temperatures have warmed over the last century, the hottest days during the Midwestern growing season have actually cooled.“还有另一个更令人惊讶的趋势有利于玉米产量。尽管上个世纪大部分地区的气温都有所上升，但中西部生长季节最热的日子实际上变冷了。”由此可知，文中提到了2个有利于玉米产量的因素。故选C。

4.

目的意图题。根据第二段中In a newspaper, researchers find that a prolonged(延长的) growing season due to increased temperatures, combined with the natural cooling effects of large fields of plants, have had a major contribution to improved corn production in the U.S.“研究人员在一份报纸上发现，由于气温升高而延长的生长季节，加上大面积种植的自然降温效应，对美国玉米产量的提高做出了重大贡献”。由此可知这篇文章介绍了一项研究结果。故选D。