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  When nature is left alone, a balance is reached among the animals and plants living in one area.But when man starts his work in nature, the balance is likely to be destroyed.He grows a crop and takes it away to eat; then there are no dead leaves to fall on the ground, holding water while it sinks into the surface, or decaying(腐烂)and adding humus(腐殖质)to the soil.Unless a farmer acts with knowledge and skill, he is therefore most likely to make the land poorer.To take the place of the useful matter in the crops that he removes, he uses some kind of fertilizer(肥料).Chemical fertilizers are of great help, but the waste products of animals and decaying remains of plants should also be put on the land.In some places, it is a habit to burn waste material lying about, but such burning destroys the useful matter in the dead plants.Although the ashes that are left are valuable when put on the land, a better practice is to bury the waste so that it decays and increases the humus in the soil.

  In the past, when the world population was much lower than it is now, a man had little difficulty in ordinary times in growing the food that was needed.When a field had been used some years and had become tired, the farmer could move to another place.The tired land then slowly recovered.Gradually grasses and other plants would appear on it and its productive power would slowly return to normal through their decay.But nature, left alone, would take a long time to bring back the land to its former state; the length of time required would depend on local conditions, but it might well be ten years.

  It is a bad practice to grow the same crop in a field year after year.If the crop is changed, the land will suffer less because it is treated and used in a different way.Different plants have different effects on the soil.Therefore, a change of crop will do less harm than the growing of the same crop year after year and a regular change to grass will do good to the soil.Much will therefore be gained if different crops are grown one after another, a method known as the rotation(轮作)of crops.

(1)

According to the passage, the land will become poorer ________.

[  ]

A.

if all the dead leaves are cleared away

B.

if the humus is increased after the harvest

C.

if dead leaves decay in the soil by themselves

D.

if waste plant material lying about is buried

(2)

We can learn from the passage that the tired land has gradually recovered ________.

[  ]

A.

when grasses and other plants appear again

B.

when the treatment is given by nature alone

C.

after new grasses and other plants have decayed again

D.

after nature has been left alone for several months

(3)

A modern farmer can hardly move to another place as he did before because ________.

[  ]

A.

the productive power of a new field isn’t higher than that of an old one

B.

there are few free fields left for him to do farming

C.

it takes a farmer more than ten years to start farming in a new field

D.

there will be too many grasses in a new field to grow crops

(4)

It is most likely that the author will go on to ________ in the paragraph following the passage above.

[  ]

A.

introduce other methods of planting crops

B.

deal with how to prevent land getting tired

C.

start another topic of how to make use of land

D.

further explain what the rotation of crops is

答案:1.A;2.C;3.B;4.D;
解析:

(1)

从“then there are no dead leaves to fall on the ground到he is therefore most likely to make the land poorer”可以分析出这个答案。

(2)

信息来自Gradually grasses and other plants would appear on it and its productive power would slowly return to normal through their decay。

(3)

信息来自“In the past, when the world population was much lower than it is now”。

(4)

作者在文章中提出了土地肥力下降的问题,给出了解决的办法,如秸秆归田,最后提出了轮作的概念,按照上面的写作特点,应该继续详细说明有关轮作的方法。


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科目:高中英语 来源:设计必修一英语北师版 北师版 题型:050

阅读理解

How Long Can People Live?

  She took up skating at age 85, made her first movie appearance at age 114, and held a concert in the neighborhood on her 121st birthday.

  Whe n it comes to long life, Jeanne Calment is the world’s recordholder.She lived to the ripe old age of 122.So is 122 the upper limit to the human life span(寿命)?If scientists come up with some sort of pill or diet that would slow aging, could we possibly make it to 150-or beyond?

  Researchers don’t entirely agree on the answers.“Calment lived to 122, so it wouldn’t surprise me if someone alive today reaches 130 or 135,”says Jerry Shay at the University of Texas.

  Steve Austad at the University of Texas agrees.“People can live much longer than we think,”he says.“Experts used to say that humans couldn’t live past 110.When Calment blew past that age, they raised the number to 120.So why can’t we go higher?”

  The trouble with guessing how old people can live to be is that it’s all just guessing.“Anyone can make up a number,”says Rich Miller at the University of Michigan.“Usually the scientist who picks the highest number gets his name in Time magazine.”

  Won’t new anti-aging techniques keep us alive for centuries?Any cure, says Miller, for aging would probably keep most of us kicking until about 120.Researchers are working on treatments that lengthen the life span of mice by 50 percent at most.So, if the average human life span is about 80 years, says Miller,“adding another 50 percent would get you to 120.”

  So what can we conclude from this little disagreement among the researchers?That life span is flexible(有弹性的),but there is a limit, says George Martin of the University of Washington.“We can get flies to live 50 percent longer,”he says.“But a fly’s never going to live 150 years.”

  “Of course, if you became a new species(物种),one that ages at a slower speed, that would be a different story,”he adds.

  Does Martin really believe that humans could evolve(进化)their way to longer life?“It’s pretty cool to think about it,”he says with a smile.

(1)

What does the story of Jeanne Calment prove to us?

[  ]

A.

People can live to 122.

B.

Old people are creative.

C.

Women are sporty at 85.

D.

Women live longer than men.

(2)

According to Steve Austad at the University of Texas, ________.

[  ]

A.

the average human life span could be 110

B.

scientists cannot find ways to slow aging

C.

few people can expect to live to over 150

D.

researchers are not sure how long people can live

(3)

Who would agree that a scientist will become famous if he makes the wildest guess at longevity?

[  ]

A.

Jerry Shay.

B.

Steve Austad

C.

Rich Miller

D.

George Martin

(4)

What can we infer from the last three paragraphs?

[  ]

A.

Most of us could be good at sports even at 120.

B.

The average human life span cannot be doubled.

C.

Scientists believe mice are aging at a slower speed than before.

D.

New techniques could be used to change flies into a new species.

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