In the atmosphere, carbon dioxide acts rather like a one-way mirror or the glass in the roof of a greenhouse which allows the sun's rays to enter but prevents the heat from escaping.

　　 According to a weather expert' s prediction, the atmosphere will be 3℃ warmer in the year 2050 than it is today, if man continues to burn fuels at the present rate. If this warming up took place, the ice caps in the poles would begin to melt, thus raising sea level several metres and severely flooding coastal cities. Also, the increase in atmospheric temperature would lead to great changes in the climate of the northern hemisphere (北半球), possibly resulting in an alteration of the earth's chief food growing zones.

　　  In the past, concern about a man-made warming of the earth has concentrated on the Arctic because the Antarctic is much colder and has a much thicker ice sheet. But the weather experts are now paying more attention to West Antarctic, which may be affected by only a few degrees of warming, in other words, by a warming on the scale that will possibly take place in the next fifty years from the burning of fuels.

　　  Satellite pictures show that large areas of Antarctic ice are already disappearing. The evidence available suggests that a warming has taken place. This fits the theory that carbon dioxide warms the earth.

　　  However, most of the fuel is burnt in the northern hemisphere, where temperatures seem to be falling. Scientists conclude , therefore, that up to now natural influences on the weather have gone beyond those caused by man. The question is: Which natural cause has most effect on the weather?

　　  One possibility is the variable behavior of the sun. Astronomers at one research station have studied the hot spots and "cold" spots (that is, the relatively less hot spots) on the sun. As the sun rotates (使旋转), every 27. 5 days, it presents hotter or "colder" faces to the earth, and different aspects to different parts of the earth. This seems to have a considerable effect on the distribution of the earth's atmospheric pressure, and consequently on wind circulation. The sun is also changeable over a long term: its heat output goes up and down in cycles, the latest trend being downward.

　　  Scientists are now finding shared relations between models of solar weather interactions and the actual climate over many thousands of years, including the last Ice Age. The problem is that the models are predicting that the world should be entering a new Ice Age and it is not. One way of solving this theoretical difficulty is to assume a delay of thousands of years while the solar effects overcome the inertia (惯性) of the earth's climate. If this is right, the warming effect of carbon dioxide might thus be serving as a useful opposed balance to the sun's fading heat .

66. It can be concluded that a concentration of carbon dioxide in the atmosphere would_________.

   A. mean a warming-up in the Antarctic

   B. raise the temperature of the earth' s surface

C. prevent the sun's rays from reaching the earth's surface

D. explain the cause of  great changes in the climate in the northern hemisphere

67.The article was written to explain ___________. 

A. the greenhouse effect

B. the solar effects on the earth

C. the causes affecting weather

D. the models of solar-weather interactions

68. Although the fuel consumption is greater in the northern hemisphere, temperatures there　seem to be falling. This is__________.

 A. mainly because the levels of carbon dioxide are rising

 B. partly due to changes in the output of solar energy

C. possibly because the ice caps in the poles are melting

D. only due to the effect of the inertia of the earth' s climate

69. On the basis of their models, scientists believe the opinion that__________.

A. the climate of the world should be becoming cooler

B. the new Ice Age will be delayed by the greenhouse effect

C. the man-made warming effect helps to increase the solar effects

D. it will take thousands of years for the inertia of the earth's climate to take effect

70. If the assumption about the delay of a new Ice age is correct, ____________.

A. ice would soon cover the northern hemisphere

B. the greenhouse effect could work in favor of the earth

C. the best way to overcome the cooling effect would be to burn more fuels

D. the increased levels of carbon dioxide in the atmosphere could warm up the earth even more quickly

In the atmosphere, carbon dioxide acts rather like a one-way mirror or the glass in the roof of a greenhouse which allows the sun's rays to enter but prevents the heat from escaping.

　　 According to a weather expert' s prediction, the atmosphere will be 3℃ warmer in the year 2050 than it is today, if man continues to burn fuels at the present rate. If this warming up took place, the ice caps in the poles would begin to melt, thus raising sea level several metres and severely flooding coastal cities. Also, the increase in atmospheric temperature would lead to great changes in the climate of the northern hemisphere (北半球), possibly resulting in an alteration of the earth's chief food growing zones.

　　  In the past, concern about a man-made warming of the earth has concentrated on the Arctic because the Antarctic is much colder and has a much thicker ice sheet. But the weather experts are now paying more attention to West Antarctic, which may be affected by only a few degrees of warming, in other words, by a warming on the scale that will possibly take place in the next fifty years from the burning of fuels.

　　  Satellite pictures show that large areas of Antarctic ice are already disappearing. The evidence available suggests that a warming has taken place. This fits the theory that carbon dioxide warms the earth.

　　  However, most of the fuel is burnt in the northern hemisphere, where temperatures seem to be falling. Scientists conclude , therefore, that up to now natural influences on the weather have gone beyond those caused by man. The question is: Which natural cause has most effect on the weather?

　　  One possibility is the variable behavior of the sun. Astronomers at one research station have studied the hot spots and "cold" spots (that is, the relatively less hot spots) on the sun. As the sun rotates (使旋转), every 27. 5 days, it presents hotter or "colder" faces to the earth, and different aspects to different parts of the earth. This seems to have a considerable effect on the distribution of the earth's atmospheric pressure, and consequently on wind circulation. The sun is also changeable over a long term: its heat output goes up and down in cycles, the latest trend being downward.

　　  Scientists are now finding shared relations between models of solar weather interactions and the actual climate over many thousands of years, including the last Ice Age. The problem is that the models are predicting that the world should be entering a new Ice Age and it is not. One way of solving this theoretical difficulty is to assume a delay of thousands of years while the solar effects overcome the inertia (惯性) of the earth's climate. If this is right, the warming effect of carbon dioxide might thus be serving as a useful opposed balance to the sun's fading heat .

It can be concluded that a concentration of carbon dioxide in the atmosphere would_________.

   A. mean a warming-up in the Antarctic

   B. raise the temperature of the earth' s surface

C. prevent the sun's rays from reaching the earth's surface

D. explain the cause of  great changes in the climate in the northern hemisphere

The article was written to explain ___________.

A. the greenhouse effect

B. the solar effects on the earth

C. the causes affecting weather

D. the models of solar-weather interactions

Although the fuel consumption is greater in the northern hemisphere, temperatures there　seem to be falling. This is__________.

A. mainly because the levels of carbon dioxide are rising

 B. partly due to changes in the output of solar energy

C. possibly because the ice caps in the poles are melting

D. only due to the effect of the inertia of the earth' s climate

On the basis of their models, scientists believe the opinion that__________.

A. the climate of the world should be becoming cooler

B. the new Ice Age will be delayed by the greenhouse effect

C. the man-made warming effect helps to increase the solar effects

D. it will take thousands of years for the inertia of the earth's climate to take effect

If the assumption about the delay of a new Ice age is correct, ____________.

A. ice would soon cover the northern hemisphere

B. the greenhouse effect could work in favor of the earth

C. the best way to overcome the cooling effect would be to burn more fuels

D. the increased levels of carbon dioxide in the atmosphere could warm up the earth even more quickly

D
　　Beyond two or three days，the world’s best weather forecasts are doubtful, and beyond six or seven they are worthless.
　　The Butterfly Effect is the reason. For small pieces of weather—to a global forecaster，small can mean thunder—storms and blizzards（暴风雪）—any prediction becomes worse rapidly. Errors and uncertainties increase，from dust devils and storms up to continent-size eddies（旋涡）that only satellites can see.
　　The modern weather models work with net-like points sixty miles apart，and even so，some starting data have to be guessed，since ground stations and satellites cannot see everywhere. But suppose the earth could be covered with sensors placed one foot apart，rising at one-foot intervals all the way to the top of the atmosphere. Suppose every sensor gives perfectly accurate readings of temperature，pressure，humidity（温度）, and any other data a weatherman would want. Exactly at noon a powerful computer takes all the data and calculates what will happen at each point at 12.01, then 12.02，then 12.03…the computer will still be unable to predict whether Princeton will have sun or rain one month away. At noon the spaces between the sensors will hide fluctuations（波动）that the computer will not know about. By 12.01，those fluctuations will already have created small errors one foot away. Soon the errors will have added to the ten-foot scale，and so on up to the size of the globe.
63．A weather forecast ____________ in the world.
A．is reliable within one or two days
B．is doubtful beyond 24 hours
C．becomes useless beyond two or three days
D．is still worthwhile in seven days
64．Usually there is a weather sub-station____________.
A．in every city 　　　　　　　　　　B．every 60 miles
C．between two cities 　　　　　　　 D．every one foot
65．Which of the following statements is true？
A．People have not placed sensors one foot apart in the atmosphere.
B．Scientists have already put sensors one foot apart in the world.
C．Every sensor gives perfectly accurate data a weatherman wants.
D．Ground weather stations and satellites can see every place on earth.
66．Our computer will not be able to know about fluctuations because ____________.
A．the sensors are not good enough
B．they are hidden by the spaces between the sensors
C．they are too far away
D．they move very fast

Uh­oh, the new year's just begun and already you're finding it hard to keep those resolutions to junk the junk food，get off the couch or kick smoking. There's a biological reason why a lot of our bad habits are so hard to break—they get deep­rooted in our brains.

That's not an excuse to give up. Understanding how unhealthy behaviors become deep­rooted has scientists learning some tricks that may help good habits replace the bad.“Why are bad habits stronger? You're fighting against the power of an immediate reward. We all as creatures give greater value to an immediate reward than something that's delayed，” says Dr Nora Volkow, director of the National Institute on Drug Abuse.

Just how that bit of happiness turns into a habit involves a pleasure­sensing chemical named dopamine(多巴胺). It trains the brain to want that reward again and again—increasing the connection each time—especially when it gets the right cue(暗示) from your environment.

People tend to overestimate their ability to resist temptations around them, thus destroying attempts to get rid of bad habits. Even scientists who recognize it find it hard to resist.“I don't like popcorn. But every time I go to the cinema, I have to eat it，” Volkow says.“It's fascinating.”

A movement to pay people for behavior changes may make use of that connection, as some companies offer employees immediate payments for adopting better habits. However paying for behavior turns out, researchers say there are some steps that may help counter your brain's hold on bad habits: repeat，repeat，repeat the new behavior—the same routine at the same time of day. Determined to exercise？Doing it at the same time of the morning makes the brain recognize the habit eventually. If you don't do it, you feel awful. Exercise itself raises dopamine levels, so eventually your brain will get a feel­good hit even if your muscles protest. Reward yourself with something you really desire, Volkow stresses. You exercised all week? Stuck to your diet? Buy a book, a great pair of jeans, or try a fancy restaurant.

20．What's the subjective reason for being hard to break bad behaviors?

A．Some behaviors get deep­rooted in our brains.

B．We prefer an immediate reward.

C．We value delayed gifts.

D．We are all creatures of nature.

21．What does the underlined word “connection” in Paragraph 3 refer to?

A．Pleasure and behavior.  　B．Brain and reward.

C．Happiness and dopamine.  　D．Cue and environment.

22．It can be inferred that the higher the dopamine level is，________．

A．the harder it is for you to break the bad habit

B．the less pleasure you will get

C．the stronger bad habits will become

D．the more you'll want to get a reward

23．Why does Volkow eat popcorn even though he doesn't like it?

A．Because he recognizes the importance of him.

B．Because it is needed for normal growth of the body.

C．Because he can't resist the temptation of it.

D．Because it makes him relaxed to eat popcorn while seeing films.