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Damage to Ozone Layer Gets Worse

    In the middle of winter, when snow is falling in many parts of the United States, scientists have sounded a warning to people who plan to spend many hours in the sun this summer．The warning: The sun's summertime rays are more dangerous than once thought.

    A team of scientists from 80 nations recently reported to the United Nations that a layer of ozone（臭氧層）in the atmosphere, which protects humans from harmful levels of ultraviolet（紫外線）radiation, will be thinner over the United States this summer．The thinner layer allows more ultraviolet rays from the sun to reach Earth．The extra amount of ultraviolet radiation could cause an increase in the number of cases of skin cancer.

    Scientists first became concerned about the layer in the mid-1980s when a hole was discovered in the layer above Antarctica during the winter．The hole was caused in chemicals used in refrigerators and air conditioners．When these chemicals are sent out into the atmosphere, they produce gases that destroy the ozone.

    Concern about the protective ozone layer rose more recently when data from satellites and ground stations showed that ozone levels were dropping over areas other than Antarctica．Low ozone levels were recorded in the spring and summer over the United States and over other populated areas in the world.

    Although many countries have already begun stopping the use of ozone-destroying chemicals, the new findings are expected to advance the timetable for a total ban of the chemicals.

1.The scientists have observed the ozone layer ______．

    A．since 1980                     B．since last winter

    C．for more than 20 years            D．for about one year

2.The ozone layer in the atmosphere can ______.

    A．do a lot of good to human beings in many ways

    B．protect humans from diseases caused by bad weather

    C．do a lot of harm to human beings in the summer-time

    D．protect humans from harmful levels of ultraviolet radiation

3.Scientists first found that there was a hole in the ozone layer ______.

    A．a(chǎn)bove Arctic during the winter in the mid-1980s

    B．a(chǎn)bove Antarctica during the winter in the mid-1980s

    C．over somewhere in the north of the equator in 1980

    D．over the USA in the summertime in the mid-1980s

4.The damage to the ozone layer was caused by ______.

    A．the changeable weather          B．ozone-destroying chemicals

C．chemicals from refrigerators      D．chemicals from air conditioners

Plants are flowering faster than scientists predict in reaction to climate change, which could have long damaging effects on food chains and ecosystems.

“Global warming is having a great effect on hundreds of plant and animal species around the world, changing some living patterns.” scientists say.

Increased carbon dioxide (CO2) in the air from burning coal and oil can have an effect on how plants produce oxygen, while higher temperatures and changeable rainfall patterns can change their patterns of growth.

“Predicting species’ reaction to climate change is a major challenge in ecology,” said the researchers of several U.S. Universities. They said plants had been the key object of study because their reaction to climate change could have an effect on food chains and ecosystem services.

The study, published on the Nature website, uses the findings from plant life cycle studies and experiments across four continents and 1,634 species. It found that some experiments had underestimated the speed of flowering by 8.5 times and leafing by 4 times.

“Across all species, the experiments underestimated the speed of the advance—for both leafing and flowering—that results from temperature increases,” the study said.

“The design of future experiments may need to be improved to better predict how plants will react to climate change,” it said.

Plants are necessary for life on the Earth. They are the base of the food chain, using photosynthesis (光合作用) to produce sugar from carbon dioxide and water. They let out oxygen which is needed by nearly every organism on the planet.

Scientists believe the world’s average temperature has risen by about 0.8 ℃ since 1900, and nearly 0.2 ℃ every ten years since 1979.

So far, efforts to cut emissions of planet-warming greenhouse gases are not seen as enough to prevent the Earth heating up beyond 2 ℃ this century—a point scientists say will bring the danger of a changeable climate in which weather extremes are common, leading to drought, floods, crop failures and rising sea levels.

1.What is the key information the author wants to give in Paragraph 1?

A. The increasing speed of flowering is beyond scientists’ expectation.

B. Climate change leads to the change of food production patterns.

C. Plants’ reaction to weather could have damaging effects on ecosystem.   

D. Food chains have been seriously damaged because of weather.

2.We can learn from the study published on the Nature website that _____.    

A. scientists should improve the design of the experiments

B. plants’ flowering is 8.5 times faster than leafing

C. there are 1,634 plant species on the four continents

D. the experiments failed to predict how plants react to climate change

3.Scientists pay special attention to the study of plants because _____.     

A. they can prove the climate change clearly

B. they are very important in the food chains

C. they play a leading role in reducing global warming

D. they are growing and flowering much faster than before

4.What can be inferred from the last two paragraphs about the world’s temperature?    

A. It has risen nearly 0.2 ℃ since 1979.

B. It is 0.8 ℃ higher in 1979 than that of 1990. 

C. It needs to be controlled within 2 ℃ in this century.

D. Its change will lead to weather extremes.

She wrote a month ago, ______ we’ve heard nothing.

A. since when B. before whichC. since thatD. after which

It will be many years ______ the doctors and medical scientists can find _____ for cancer.

    A . since; cures              B. when; treatments 

C. before; cures             D. until; treaments

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