It was once thought that air pollution affected only the area immediately around large cities with factories and heavy automobile traffic.Today, we know that although these are the areas with the worst air pollution，the problem is literally worldwide.On several occasions over the past decade，a heavy cloud of air pollution has covered the entire eastern half of the United States and led to health warnings even in rural areas away from any major concentration of manufacturing and automobile traffic.In fact， the very climate of the entire earth may be affected by air pollution.

　　Some scientists feel that the increasing concentration of carbon dioxide in the air resulting from the burning of fossil fuels(coal and oil)is creating a“greenhouse effect”-holding in heat reflected from the earth and raising the world’s average temperature.If this view is correct and the world’s temperature is raised only a few degrees。much of the polar ice cap will melt and cities such as New Y0rk，Boston，Miami，and New Orleans will be under water.

　　Another view, less widely held，is that increasing particulate matter in the atmosphere is blocking sunlight and lowering the earth’s temperature—a result that would be equally disastrous.A drop of just a few degrees could create something close to new ice age and would make agriculture difficult or impossible in many of our top farming areas.

　　At present we do not know for sure that either of these conditions will happen，though one recent government report prepared by experts in the field concluded that the greenhouse effect is very likely.Perhaps，if we are very lucky, the two tendencies will offset each other and the world’s temperature will stay about the same as it is now.

　　56.According to the passage，people today think that air pollution________.

　　A)exists merely in urban and industrial areas

　　B)may have an effect on the entire earth

　　C)causes widespread damage in the countryside

　　D)is not so serious as it used to be

　　57.The“greenhouse effect” results from________.

　　A)the concentration of carbon dioxide in the air

　　B)the increasing particulate matter in the atmosphere

　　C)the burning of firewood

　　D)the blocking of sunlight

　　58.What does the author think of the possibility of a new ice age?

　　A)He rejects it as being ungrounded.

　　B)He holds the same view.

　　C)He is uncertain of its occurrence.

　　D)He thinks that would happen soon.

　　59.The word“offset”(Line 3，Para.4)means________.

　　A)slip into

　　B)catch up with

　　C)set up

　　D)make up for

　　60.The passage is mainly about__________.

　　A)the potential effect of air pollution

　　B)the possibility of a new ice age

　　C)the effects of global warming

　　D)the causes of climate change

　　Questions 61 t0 65 are based on the following passage.

　　Becker had one occasional anxiety：the suspicion that he owned more than would fit comfortably into the case.The feeling，when it came，was the signal for him to throw something away or just leave it lying about.This was the automatic fate of his worn—out clothes for example.Having no use for choice or variety,he kept just a raincoat，a suit，a pair of shoes and a few shirts，socks and so on，no more in the clothing line.He bought and read many books，and left them wherever he happened to be sitting when he finished them.They quickly found new owners.

　　Becker was a professional traveler, interested and interestin9.He was not one t0 “do” a country in a week or a city in three days.He liked to get the feel of a place by living in it，reading its newspapers，watching its TV and discussing its affairs.He always tried to make a few friends，if necessary even by stopping a suitable—looking person in the street and talking to him.It worked well in about one case inten.Though Becker’s health gave him no cause for alarm，he made.a point of seeing a doctor as soon as he arrived anywhere.“A doctor knows a place and its people better than anyone，”he used to say.

　　He never went to see a doctor，he always sent for one，that，he found，was the quickest way to gain confidences，which came out freely as soon as he mentioned that he was a writer.

　　Becker was an artist as well.He painted pictures of his places and，when he had gathered enough information，he wrote about them.He sold his work，through an agent，to newspapers and magazines.It was an agreeable sort of life for a good social mixer, lived nearly always in fine weather, and as Becker never stayed anywhere for long，he enjoyed the satisfying advantage of paying very little in tax.

　　61.According to the passage，the anxiety of Becker was__________.

　　A)the doubt that he owned too much clothes B)the thought of having too much baggage

　　C)the miserable fate of his worn out clothes D)the decline in his memory

　　62.What is the fate of Becker’s books?

　　A)They were kept in his case.

　　B)They were sent to his friends.

　　C)They were donated to others in need.

　　D)They were left anywhere.

　　63.Becker would see a doctor as he arrived at a new place because__________.

　　A)his health was in danger

　　B)he wanted to make friends with the doctor

　　C)he intended to get confidences from the doctor

　　D) he wanted to know the place and its people through the doctor

　　64.How did Becker feel about taxation?

　　A)He was pleased he only had to pay little.

　　B)He felt ashamed of not paying taxes.

　　C)He worried about it，so he moved from one place to another.

　　D)He hated it so much that he broke the tax laws.

　　65.Which of the following is TRUE according to the passage?

　　A)Becker was always worried about something that would not happen.

　　B)Becker kept a good many books.

　　C) Becker would talk to strangers in the street.

　　D)Becker often traveled through a country in a couple of days.