45.()cleans the blackboard should be praised.

2. Passage Twenty-FourSocial change is more likely to occur in societies where there is a mixture of different kinds of people than in societies where people are similar in many ways.The simple reason for this is that there are more different ways of looking at things present in the first kind of society.There are more ideas， more disagreements in interest， and more groups and organizations with different beliefs.In addition， there is usually a greater worldly interest and greater tolerance in mixed societies.All these factors tend to promote social change by opening more areas of life to decision.In a society where people are quite similar in many ways， there are fewer occasions for people to see the need or the opportunity for change because everything seems to be the same.And although conditions may not be satisfactory， they are at least customary and undisputed.Within a society， social changes is also likely to occur more frequently and more readily in the material aspects of the culture than in the non-material， for example， in technology rather than in values; in what has been learned later in life rather than what was learned early; in the less basic and less emotional aspects of society than in their opposites; in the simple elements rather than in the complex ones; in form rather than in substance; and in elements that are acceptable to the culture rather than in strange elements.Furthermore， social change is easier if it is gradual.For example， it comes more readily in human relations on a continuous scale rather than one with sharp dichotomies (一分为二).This is one reason why change has not come more quickly to Black American as compared to other American minorities， because of the sharp difference in “appearance between them and their white counterparts”.()is one of the factors that tend to promote social change.

49.After( )the numbers＇ in every possible combination， we finally hit on a solution.

A. 　running through

B. 　running after

C. 　running over

D. 　running out

39.The robot “teacher” was talking with his students as though it ()a human teacher.

A. 　were

B. 　was

C. 　is

D. 　had been

31.The conference ()a full week by the time it ends.

A. 　must have lasted

B. 　will have lasted

C. 　would last

D. 　has lasted

1. Passage ThirteenTrees are useful to man in three important ways: they provide him with wood and other products; they give him shade; and they help to prevent droughts and floods.Unfortunately， in many parts of the world， man has not realized that the third of these services is the most important.In his eagerness to make money from trees， he has cut them down in large numbers， only to find that without them he has lost the best friends he had.And besides， he is usually too careless to plant and look after new trees.So the forests slowly disappear.This does not only mean that man will have fewer trees.The results are even more serious: for where there are trees， their roots break up soil——allowing the rain to sink in——and also bind the soil， thus preventing it from being washed away easily; but where there are no trees， the rain falls on hard ground and flows away， causing floods and carrying away the rich topsoil.When all the topsoil is gone， nothing remains but worthless desert.Two thousand years ago a rich and powerful country cut down its trees to build warships， with which to gain itself an empire.It set up the empire but， without its trees， its soil became poor and it grew weak.When the empire fell into pieces， there is nothing left except floods and starvation.What is the most important service of trees to man according to the passage?

1. Passage SixteenJustin was always prepared.His motto was “Never throw anything out， you never know when it might come in handy.” His bedroom was so full of flat bicycle tires， bent tennis rackets， deflated basketballs， and games with missing pieces that you could barely get in the door.His parents pleaded him to clean out his room.“What use is a fish tank with a hole in the bottom?” his father asked.But Justin simply smiled and repeated his motto， “Never throw anything out， you never know when it might come in handy.”When Justin was away from home， he always carried his blue backpack.He liked to think of it as a smaller version of his bedroom——a place to store the many objects that he collected.It was so worn and stretched that it hardly resembled a backpack anymore.It was full of the kind of things that seemed unimportant， but when used with a little imagination， might come in handy.Justin had earned a reputation for figuring things out and getting people out of otherwise hopeless situations.Many of his classmates and neighbors sought him out when they needed help with a problem.On the first day of school， his friend Kenny， came looking for Justin.“Do you think you have something in your bag that could help me remember my locker combination?” he asked.“I lost the paper it was written on.I have science class in two minutes and if I’m late on the first day it’ll make me look bad for the rest of the year.” Kenny looked genuinely worried.“Relax，” Justin said， taking his backpack off and opened it.“Remember how you borrowed my notebook in homeroom to write the code down? Well， I know how we can recover what you wrote.”He took the notebook and a soft lead pencil out of his bag.The page that Kenny had written on had left faint indentations (旧凹痕)on another page in the notebook.Justin held the pencil on its side and rubbed it lightly over the indentations.Slowly but surely the numbers of the locker combination appeared in white， set off by the gray pencil rubbings.“That’s amazing!” Kenny said.“I owe you one.” And he dashed off to open his locker.Why is Justin’s room such a mess?

4. Passage Thirty-FourMuch unfriendly feeling towards computers has been based on the fear of widespread unemployment resulting from their introduction.Computers are often used as part of automated (自动化的)production systems requiring a least possible number of operators， causing the loss of many jobs.This has happened， for example， in many steelworks.On the other hand， computers do create jobs.They are more skilled and better paid， though fewer in number than those they replace.Many activities could not continue in their present form without computers， no matter how many people are employed.Examples are the check clearing (交换)system of major banks and the weather forecasting system.When a firm introduces computers， a few people are usually employed in key posts (such as jobs of operations managers)while other staff are re-trained as operators， programmers， and data preparation staff.After the new system has settled down， people in non-computer jobs are not always replaced when they leave， resulting in a decrease in the number of employees.This decrease is sometimes balanced by a substantial increase in the activity of the firm， resulting from the introduction of computers.The attitudes of workers towards computers vary.There is fear of widespread unemployment and of the takeover of many jobs by computer-trained workers， making promotion for older workers not skilled in computers more difficult.On the other hand， many workers regard the trend toward wider use of computers inevitable.They realize that computers bring about greater efficiency and productivity， which will improve the condition of the whole economy， and lead to the creation of more jobs.This view was supported by the former British Prime Minister， James Callaghan in 1954， when he made the point that new technologies hold the key to increased productivity， which will benefit the economy in the long run.According to the passage， what results from the introduction of computers?

32. Questions 31 to 35 are based on the following passage.To write his 2010 book， The 5-Factor World Diet， nutritionist Harley Pasternak traveled to the healthiest countries around the world to learn more about what made their meals extra nourishing.He noted that Japanese people ate a wonderful variety of seaweeds， and that Chinese people tried to include at least five different colors in every meal.Pasternak also came away with some valuable observations about how different the North American way of life was， compared with many other countries.For starters， Americans eat much bigger portions than people in other countries.“We don’t prioritize eating seasonally or locally， and we also add lots of salt， sugar and thickening agents to our foods，” explained Pasternak.Contrast that to the healthy Mediterranean， Nordic and Okinawan diets listed in Pasternak＇s book.They all seem to stick to the ethos (特质)of regional， seasonal produce.For example， a traditional Mediterranean diet includes fruits， vegetables， whole grains， nuts and olive oil as the main components of nutritional intake.Fish， chicken and red wine make moderate appearances， while red meat， salt and sugar are used much less often.The benefits of a traditional Mediterranean diet have been studied since the 1970s， and researchers have found that living that olive oil life can help people lose weight， lower their heart disease risk and reverse diabetes.Most other healthy eating cultures also make meals an event—say， multiple courses around the family table， or a glass or two of red wine at a long lunch—opposed to hastily wolfing down handfuls of cereal above the kitchen sink and calling it dinner.Each of the healthy eating cultures has its own unique feature.But Pasternak did take note of one unifying factor in all of the healthy societies he observed.“The only overlapping feature in most of these healthy countries is that they all walk way more than the average American，” said Pasternak.“So really， regardless of what you’re eating， if someone’s walking four miles more than you each day， they are going to be a lot thinner and live a lot longer than you.”What is typical of Americans in the way of eating?

A. 　They emphasize nutrition.C)They prioritize convenience.

B. 　They tend to eat quite a lot.D)They care about flavors.

C. 　They prioritize convenience.

D. 　They care about flavors.

37.She earns a good salary， so she ()be deep in debt.

A. 　can’t

B. 　must

C. 　needn’t

D. 　should

44.Americans eat ()vegetables per person today as they did in 1910.

A. 　more than twice

B. 　as twice as many

C. 　twice as many as

D. 　more than twice as many