2. 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.Why do forests in many parts of the world slowly disappear?

3. 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.How does Justin help his friends?

4. Passage TenNowadays， children heavily cling to digital devices such as computers and smart phones.Some spend up to six hours a day on their digital devices.They can be playing games online with people elsewhere， updating their status on social media， texting friends， or looking for the latest apps to download to their computers or smart phones.This worried Martin Strott.He is the headmaster of the Old Hall School in Wellington， England.He was so concerned that he challenged his students to take part in a week of (“digital detox”)， a program to reduce their reliance on digital devices.Mr.Strott told the local newspaper， the Shropshire Star， that too much screen time would affect the development of their social skills.At another interview with a magazine， he mentioned that this over-reliance on digital devices “takes away family time and reduces their chances of face-to-face communication”.The parents are happy with the program.But what about the children? Nine-year-old Fred usually spends around two hours on his digital devices at home after school and around 12 hours on weekends.For him， the digital detox experience was “really hard”.He said that he had been engaged in many interesting outdoor activities organized by the headmaster， but still missed his phone and online games.The idea of keeping children away from their digital devices for a while to prevent too much dependence on them is not particularly new.There have been similar practices in the United States.But are they effective in the long run? According to Mr.Strott， even if kids go back to their digital devices， the hope is that at least they will think about how they will use their time.How did Fred feel about his “digital detox” experience?

43.I fell down and broke three of my teeth.I wonder how many times I have to come
here and get my false teeth ().

A. 　fix

B. 　fixing

C. 　fixed

D. 　to fix

32.Had he worked harder， he ()the exams.

A. 　must have got through

B. 　would have got through

C. 　permitted are freshmen

D. 　are permitted freshmen

40.Theory is based on practice and ()serves practice.

A. 　in turn

B. 　in tone

C. 　in return

D. 　in practice

15.Corn originated in the New World and thus was not known in Europe until Columbus found it ()in Cuba.

A. 　being cultivated

B. 　been cultivated

C. 　having cultivated

D. 　cultivating

1. 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”.The passage has mainly discussed ().

32.Things might have been much worse if the mother ()on her right to keep the baby.

A. 　has been insisting

B. 　had insisted

C. 　would insist

D. 　insisted

5. Passage Twenty-SevenOut of all the students who enroll in a massive open online course (MOOC)， only about 5 percent complete the course and receive a certificate of accomplishment.This statistic is often cited as evidence that MOOCs are fatally flawed (有缺陷的)and offer little educational value to most students.Yet more than 80 percent of students who fill out a post-course survey say they met their primary objective.How do we look at these two facts? We’re used to focusing on completion rates in higher education， but they’re not the only—or even the most meaningful—indicator of engagement in open online courses.With no cost to enroll， no punishment for dropping out， and little reward for actually earning a certificate， MOOCs are fundamentally different from traditional classes—and students use them in fundamentally different ways.Data from more than 1.8 million students enrolled in 36 MOOCs offered by the University of Pennsylvania show that students treat MOOCs like a buffet (自助餐)， sampling the material according to their interests and career goals.Some are curious about the subject matter and just watch one or two video lectures; others use the discussion forums to connect with their intellectual peers around the world.Of all enrolled students， nearly 60 percent watch at least one video， complete at least one assignment， or post at least once in a forum.So focusing on the tiny fraction of students who complete a MOOC is misguided.The more important number is the 60 percent engagement rate.Students may not finish a MOOC with a certificate of accomplishment， but the courses nonetheless meet the educational goals of millions.What is the author’s attitude toward MOOCs?

11.()she realized it was too late to go home.

A. 　No sooner it grew dark than

B. 　Hardly did it grow dark that

C. 　Scarcely had it grown dark than

D. 　It was not until dark that