4、If the earth were spinning just like a rubber ball， there would only be day and night on earth， but no seasons， and days would always be the same length as nights --- 12 hours each.But this is not how the earth spins.It spins with its axis tilted(倾斜).Its axis is always at the angle(角度)to the plane of its orbit(地球的轨道平面)--- an angle of about 231/2 degrees.It is this tilting that accounts for(说明，解释清楚)our four seasons and the lengthening and shortening of days and nights.For this reason also， the Equator(赤道)(an imaginary line (一条想象出来的线)drawn around the earth at equal distance from the two poles)is not always directly under the sun’s rays.For six months the earth is tilted towards the sun， and the Northern Hemisphere(北半球)gets more than its share(份量)of sunlight every day.Days are longer than nights， and what is more， the sun’s rays come down more perpendicularly(垂直地，直射地)instead of slanting down(斜射).

7.Our son doesn＇t know what to()at the university; he can＇t make up his mind about his
future.

A. 　take in

B. 　take up

C. 　take over

D. 　take after

31.In the densely ()part of the country， the problem of air pollution must be solved.

A. 　populous

B. 　population

C. 　popular

D. 　populated

4. Passage Twenty-SixToday just as technology changed the face of industry， farmers have undergone an “agricultural revolution”.On the farm of today， machines provide all the power.One of the most important benefits will be the farm computer.A few forward-looking farmers are already using computers to help them run their farms more efficiently.The computers help them keep more accurate records， so they can make better decisions on what crops to plant， how much livestock to buy， when to sell their products， and how much profit they can expect.Many computer companies have been developing special computer programs just for farmers.Programs are being written for hog (猪)producers， grain farmers， potato farmers， and dairy farmers.In the future， farmers will be able to purchase computer programs made to their needs.Because of the growing importance of computers on the farm， students at agricultural colleges are required to take computer classes in addition to their normal agricultural courses.There can be no doubt that farmers will rely on computers even more in the future.While the old-time farm depended on horse power， and modern farms depend on machine power， farms of the future will depend on computer power.Another technological advance which is still in the experimental stage is the robot， a real “mechanized hired hand” that will be able to move and， in some ways， think like a human being.Agricultural engineers believe that computer-aided robots will make startling changes in farming before the end of the century.Unlike farmers of the present， farmers of the future will find that many day-to-day tasks will be done for them.Scientists are now developing robots that will be able to shear (修剪)sheep， drive tractors， and harvest fruit.Even complex jobs will be done by robots.For example， in order to milk their cows， farmers must first drive them into the special barn (畜棚)， then connect them to the milking machines， watch the machines， and disconnect them when they are finished.In the future， this will all be done by robots.In addition， when the milking is completed， the robots will automatically check to make sure that the milk is pure.The complete mobilization of the farm is far in the future， but engineers expect that some robots will be used before long.According to the engineers， ()will be done by robots in the near future.

47.Scarcely ()when the murderer shot him down.

A. 　did he finish his opening address

B. 　he did finish his opening address

C. 　had he finished his opening address

D. 　he had finished his opening address

39.The police are suspicious ()making plans for the summer vacation.

A. 　to

B. 　at

C. 　on

D. 　of

36.I make notes in the back of my diary()things to be mended or replaced.

A. 　by

B. 　in

C. 　with

D. 　of

47.The best way to make friends is to start a conversation with someone and ()what your common interests are and go from there.

A. 　lead to

B. 　lay down

C. 　keep on

D. 　find out

3. Passage Thirty-ThreeWe all know that DNA has the ability to identify individuals but， because it is inherited， there are also regions of the DNA strand which can relate an individual to his or her family (immediate and extended)， tribal group and even an entire population.Molecular Genealogy (宗谱学)can use this unique identification provided by the genetic markers to link people together into family trees.Pedigrees (家谱)based on such genetic markers can mean a breakthrough for family trees where information is incomplete or missing due to adoption， illegitimacy or lack of records.There are many communities and populations which have lost precious records due to tragic events such as the fire in the Irish courts during Civil War in 1921 or American slaves for whom many records were never kept in the first place.The main objective of the Molecular Genealogy Research Group is to build a database containing over 100，000 DNA samples from individuals all over the world.These individuals will have provided a pedigree chart of at least four generations and a small blood sample.Once the database has enough samples to represent the world genetic make-up， it will eventually help in solving many issues regarding genealogies that could not be done by relying only on traditional written records.Theoretically， any individual will someday be able to trace his or her family origins through this database.In the meantime， as the database is being created， molecular genealogy can already verify possible or suspected relationships between individuals.“For example， if two men sharing the same last name believe that they are related， but no written record proves this relationship， we can verify this possibility by collecting a sample of DNA from both and looking for common markers (in this case we can look primarily at the Y chromosome (染色体)，” explains Ugo Perego， a member of the BYU Molecular Genealogy research team.The Molecular Genealogy Research Group is building a database for the purpose of ().

34. Questions 31 to 35 are based on the following passage.Lao Zi once said， “Care about what other people think and you will always be their prisoner.” People-pleasing， or seeking self-worth through others’ approval， is unproductive and an exhausting way to go through life.Why do we allow what others think of us to have so much power over how we feel about ourselves? If it’s true that you can’t please people all the time， wouldn’t it make sense to stop trying?Unfortunately， sense often isn’t driving our behavior.For social beings who desire love and belonging， wanting to be liked， and caring about the effect we have on others， is healthy and allows us to make connections.However， where we get into trouble is when our self-worth is dependent upon whether we win someone’s approval or not.This need to be liked can be traced back to when we were children and were completely dependent on others to take care of us: Small children are not just learning how to walk and communicate， they are also trying to learn how the world works.We learn about who we are and what is expected of us based on interactions with others， so， to a four-year-old， if Mommy or Daddy doesn’t like him or her， there is the danger that they will abandon them.We need to understand that when we desperately want someone to approve of us， it’s being driven by that little kid part of us that is still terrified of abandonment.As you become more capable of providing yourself with the approval you seek， your need for external validation will start to vanish， leaving you stronger， more confident， and yes， happier in your life.Imagine how much time we lose each moment we restrain our authentic selves in an effort to be liked.If we base our worth on the opinions of others， we cheat ourselves of the power to shape our experiences and embrace life not only for others but also for ourselves， because ultimately， there is no difference.So embrace the cliché (老话)and love yourself as it’s highly doubtful that you’ll regret it.What can we do when we become better able to provide ourselves with the desired approval?

A. 　Enjoy a happier life.C)Receive more external validation.

B. 　Exercise self-restraint. D)Strengthen our power of imagination.

C. 　Receive more external validation.

D. 　Strengthen our power of imagination.

32.He ()on this essay for half an hour but he has written only about a hundred words.

A. 　was working

B. 　had worked

C. 　has been working

D. 　worked