________ in what he was reading, he didn’t see me before he almost knocked me down.

In the 1960s Professor Bolin predicted that the “greenhouse effect”, caused by an increase in the amount of carbon dioxide (CO₂) in the atmosphere, would lead to important changes in the Earth’s climate. At the time his prediction were regarded as science fiction. But it is now gradually agreed that the amount of carbon dioxide in the atmosphere will double from 0.03% to 0.06% in the next 50 years and that temperatures worldwide will rise by 2°Celsius.
Although a temperature rise of 2°may not seem significant, the local effects may be much greater: in polar regions a rise of 10°by 2025 is expected and in Northern Europe a rise of 4°. Indeed the first effects were expected to be felt before the end of the 20^th century,
But how does the “greenhouse effect”operate and why should such a tiny proportion（比例）of CO₂ have such a harmful effect? When living creatures breathe out or when things are burned, CO₂ enters the atmosphere. Until recently all of this was absorbed by plants, which converted it back into oxygen.
However, the balance of nature has been disturbed. In power stations, in factories and in our cars, we are burning more and more fossil fuels( coal, oil and natural gas ) and this produces huge quantities of CO₂---18 billion tons of it enter the atmosphere every year. Added to this, the destruction of forests means that less CO₂ can be converted into oxygen by plants. So, the amount of CO₂ in the atmosphere is increasing every year.
【小题1】Which of the following statements is true according to the passage?

In the 1950s, a family that owned a farm near Beulah, Michigan kept a bull chained to an elm (榆树). The bull paced around the tree, dragging the heavy iron chain, which led to a groove (槽) in the bark . The groove deepened over the years. Though for whatever reason, it did not kill the tree.

   After some years, the family took their bull away. They cut the chain, leaving the loop around the tree and one link hanging down.

   Then one year, agricultural disaster struck Michigan in the form of Dutch Elm Disease. All of the elms lining the road leading to the farm became infected and died. Everyone thought that the old elm would be the next.

The farm owners considered doing the safe thing: pulling it out and cutting it up into firewood before it died. But they simply could not bring themselves to do it. It was as if the old tree had become a family friend. So they decided to let nature take its course.

   Amazingly, the tree did not die. Nobody could understand why it was the only elm still standing in the county!

Plant experts from Michigan State University came out to observe the tree. They observed the scar left by the iron chain, now almost completely covered by bark. The experts decided that it was the chain that saved the elm’s life. They reasoned that the tree must have absorbed so much iron from the chain that it became immune to the virus.

　It’s said that what doesn’t kill you will make you stronger. Or, as Earnest Hemingway put it, "Life breaks us all, but afterwards, many of us are strongest at the broken places."

1.What did the family do with the elm when the agricultural disaster hit Michigan one year?

A. They invited plant experts to observe it.

B. They pulled it out and chopped it up into firewood.

C. They prevented it from being infected by the disease.

D. They did nothing and just let it be.

2.Which of the following statements is TRUE?

A. A groove formed because of natural forces.

B. The family decided to keep the tree because they had become attached to it.

C. All of the elms in Beulah, Michigan died of the disease.

D. The plant experts advised the family to chop it down.

3.What actually saved the elm?

A. The bull.   B. The groove.    C. The iron chain.  D. The experts.

4.What would be the best title for the passage?

A. Let nature take its course

B. Strengthened by our wounds

C. Constant dripping wears away a stone

D. Bend, but don’t break

In the 1960s Professor Bolin predicted that the “greenhouse effect”, caused by an increase in the amount of carbon dioxide (CO₂) in the atmosphere, would lead to important changes in the Earth’s climate. At the time his prediction were regarded as science fiction. But it is now gradually agreed that the amount of carbon dioxide in the atmosphere will double from 0.03% to 0.06% in the next 50 years and that temperatures worldwide will rise by 2°Celsius.

Although a temperature rise of 2°may not seem significant, the local effects may be much greater: in polar regions a rise of 10°by 2025 is expected and in Northern Europe a rise of 4°. Indeed the first effects were expected to be felt before the end of the 20^th century,

But how does the “greenhouse effect”operate and why should such a tiny proportion（比例）of CO₂ have such a harmful effect? When living creatures breathe out or when things are burned, CO₂ enters the atmosphere. Until recently all of this was absorbed by plants, which converted it back into oxygen.

However, the balance of nature has been disturbed. In power stations, in factories and in our cars, we are burning more and more fossil fuels( coal, oil and natural gas ) and this produces huge quantities of CO₂---18 billion tons of it enter the atmosphere every year. Added to this, the destruction of forests means that less CO₂ can be converted into oxygen by plants. So, the amount of CO₂ in the atmosphere is increasing every year.

1.Which of the following statements is true according to the passage?

2.The amount of CO₂ in the atmosphere is increasing every year because       .

3.The “greenhouse effect”refers to         

4.The underlined word“operate”in the third paragraph most probably means“      ”.

In the following two hours he was ________ the performance, because it turned out to be as wonderful as he had expected．

1. A.
   tired of
2. B.
   absorbed in
3. C.
   annoyed with
4. D.
   concerned about