吉林大学2015年考博英语真题

　　医学博士英语统一考试之后，即将迎来各院校的考博英语初试，英语考试的备考，参考历年真题是一个很重要的备考过程，今天新东方在线小编给大家整理了吉林大学2015年考博英语真题，帮助大家更好的备考，考博英语考试，一起来看看吧!

全国院校考博英语历年真题汇总

　　Part I Vocatulary and Structure (30 points)

　　Directions: There are 30 incomplete sentences in this part. For each sentence there are four choices marked A, B, C and D. Choose the ONE that best completes the sentence. Then mark the corresponding letter on the ANSWER SHEET with a single line through the center.

　　1.If you divide 7 by 3, you have 1•

　　A.left overB. left outC. left offD. left about

　　2.This ticketyou to a free meal in our new restaurant.

　　A.permitsB. entitlesC. grantsD. credits

　　3.Digging the foundation is the first of our building project.

　　A.processionB. solutionC. phaseD. achievement

　　4.1 don’t think Johnson will succeed in his new job, for he is notto do that type of work.

　　A.compatibleB. convenientC. consistent

　　5.Rain water has begun tothe roof of my house.

　　A.transferB. penetrateC. urge

　　6.There，s too great aof alcohol in Britain.

　　A.consumptionB. destructionC. absenceD.

　　7.Ronny’ s steps died away, and there was a moment ofsilence.

　　A.abundantB. ampleC. absoluteD.

　　8.The Indian wars greatlythe dangers of frontier life.

　　A. accumulatedB. challengedC. multipliedD.

　　9.The poor old woman can’ther hot water bottle.

　　A. do withoutB. do withC. do upD.

　　10.A system of strict discipline has a(n)effect on conduct.

　　A. automaticB. deliberateC. customaryD.

　　11.Theof new scientific discoveries to industrial production methods usually makes jobs easier to do.

　　A. additionB. applicationC. associationD. affection

　　12.The archaeologistthat the vase was 3500 years old.

　　A. utilizedB. upheldC. estimatedD. sustained

　　13.After doing odd jobs for a week, he got aposition as an office-boy.

　　A. permanentB. sufficientC. transparentD. universal

　　14.I feel rather at atalking to her，because she’s so clever.

　　A. mistakeB. faultC. disadvantageD. defect

　　15.The country hadswiftly into open conflict with its neighbors.

　　A. underwentB. plungedC. tightenedD. confronted

　　16.How many times did the clock?

　　A. hitB. knockC. beatD. strike

　　29.The football match was televisedfrom the Government stadium.

　　A.aliveB. liveC. lifeD. lively

　　30.trouble，I’m going to forget the whole affair.

　　A.Than rather causeB. Rather causing

　　C. Rather than causeD. Rather than caused

　　Part II Cloze (10 points)

　　Directions: There are 20 blanks in the following passage. For each blank there are four choices marked A, B, C and D. You should choose the ONE that best fits into the passage. Then mark the corresponding letter on the ANSWER SHEET with a single line through the center. Since about 1800，near the beginning of the Industrial Revolution, coal, petroleum, and gas have been used at a rapidly increasing rate. The supply of these 31 is limited, and electric power is very 32 in many places. Some scientists believe solar energy is the only 33 which can meet the world’s enormous 34 for power.

　　Great progress had been made in harnessing the sun. Not only is the sun now used in cooking, 35 it also supplies power for 36 things as beacon lights for ships and airplanes. It 37 telephone lines, portable radios, electric clocks, hearing aids, and even communication. Some homes and office buildings in the United States are now being 38 with solar energy.

　　The three most significant types of solar equipment 39 are the furnace, the still, and the cell. Solar furnaces heat water or air, 40 is then circulated through a building to make it comfortable. Solar stills are 41 important because they can provide 42 water at a relatively cheap rate. Salt can easily be 43 from sea water with a solar still. The most highly developed type of solar 44 equipment is the solar cell. Some cells are so 45 that they can turn 16 percent of the energy they receive from the sun 46 electric energy. One of the cell’s biggest advantages is 47 it can be made either small enough to carry 48 large enough to produce a current that can run an automobile. Besides, it has a very long life. It is still too expensive for the 49 consumer but when ways are 50 to produce it more cheaply, we can expect its use to be wide-spread.

　　31. A. materialsB.oresC. reservesD.fuels

　　32. A. abundantB.adequateC. scarceD.rare

　　33. A. meansB.sourceC. solutionD.resource

　　34. A. needB.desireC. necessityD.supply

　　35. A. moreoverB.besidesC. howeverD.but

　　36. A. someB.manyC. suchD.these

　　37. A. connectsB.operatesC. drivesD.manufactures

　　38. A. heatedB.burntC. equippedD.built

　　39. A. ever sinceB.no wonderC. in allD.so far

　　40. A. thatB.whatC. whichD.it

　　41. A. speciallyB.especiallyC. essentiallyD.specifically

　　42. A. freshB.healthyC. boiledD.cool

　　43. A. dissolvedB.distinguishedC. dividedD.removed

　　44. A. electricB.electronicC. powerD.heating

　　45. A. powerfulB.resourcefulC. efficientD.reliable

　　46. A. throughB.intoC. byD.with

　　47. A. howB.thatC. becauseD.which

　　48. A. butB.soC. orD.too

　　49. A. tipicalB.normalC. averageD.general

　　50. A. discoveredB.inventedC. disclosedD.revealed

　　Prat Reading Comprehension (60 points)

　　Directions: There are 6 passages in this part. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice and mark the corresponding letter on the ANSWER SHEET with a single line through the center.

　　Passage One

　　Questions 51 to 55 are based on the following passage.

　　Chose wisely when considering a partner, whether to attend church and how you look after your body. These decisions could have a significant effect on your overall life satisfaction. That’s according to a study that challenges the theory that life happiness is largely predetermined by your genes. This widely accepted “set-point” theory of happiness says that an individual’s long-term happiness tends to be stable because it depends mainly on genetic factors. The idea is based in part on studies that show identical twins have more similar level of life satisfaction than non-identical twins, and suggests that although your level of happiness may occasionally be thrown off by major life events, it will always

　　return to a set level within two years. To find out whether people really are destined for a certain level of happiness, Bruce Headey at the University of Melbourne in Australia and his team questioned people in Germany about their jobs, lifestyles and social and religious activities. They found that certain changes in lifestyle led to significant long-term changes in reported life satisfaction, rather than causing the temporary deflections in happiness that set-point theory would suggest. One of the biggest influences on a person’s happiness was their partner’s level of neuroticism.

　　Those with partners who scored highly on tests for neuroticism were more likely to unhappy一and to stay unhappy for as long as the relationship lasted. Altruism and family values also influenced long-term happiness. People whose annual survey responses changed to place a higher priority on altruistic behaviors and family goals were rewarded with

　　a long-term increase in life satisfaction. Those who prioritized career and material success, however, experienced a corresponding lasting decline. Having strong religious commitments also seemed to help in the pursuit of happiness. “People who attend church regularly seem to be happier than people are not religious,” says Headey. A person’s weight turned out to be another factor for long-term happiness, especially for women. Underweight men scored slightly lower than those with healthy weights, while women reported being significantly less happy when they were obese. Being overweight appeared to have no effect on men’s happiness.

　　Robert Cummins at Deakin University in Burood, Australia, notes that changes in happiness reported by Headey’s team could be influenced by individuals falling into or recovering from depression. The group suggests its findings may be applied to other populations, having found similar patterns, as yet unpublished, in the UK and Australia.

　　51.What opinion does the “set-point” theory about happiness hold, according to the passage?

　　A.What people choose in life has no effect on their happiness.

　　B.The fewer changes one has in his lifestyle, the more satisfied he feels.

　　C.People’s happiness is mostly predetermined by genetic factors.

　　D.Identical twins’ life satisfaction tends to stay in similar levels.

　　52.What did the studies led by Bruce Headey find?

　　A.People’s long-term life satisfaction seems to keep stable always.

　　B.Some changes in lifestyle have impacts on long-term happiness.

　　C.Changes in lifestyle cause occasional deflections of one’s happiness level.

　　D.People in Germany are happier than in the UK and Australia.

　　53.What action is good for people getting long-term life happiness according to Headey9s study?

　　A.Putting career and material wealth in the first place.

　　B.Going to church with family members once in a while.

　　C.Living with a partner with highly-scored neuroticism.

　　D.Prioritising altruism and family values in their life..

　　54.What does Robert Cummins want to express?

　　A.There is no scientific evidence to support the finding of Headey’s team.

　　B.There is still another factor affecting the changes in life happiness.

　　C.What Headey’s team found is not suitable for other populations but Germans.

　　D.The findings of Headey’s team are of little use for people’s daily life.

　　55.What does the passage mainly discuss?

　　A.Genetic factors tend to keep one’s life satisfaction stable.

　　B.People are destined to some level of life satisfaction.

　　C.Daily choices can affect long-term life satisfaction.

　　D.Being overweight influences one’s life happiness little.

　　Passage Two

　　Questions 56 to 60 are based on the following passage.

　　It is all very well to blame traffic jams，the cost of petrol and the quick pace of modem life, but maimers on the roads are becoming horrible. Everybody knows that the nicest men become monsters behind the wheel. You might tolerate the odd road hog, the rude and inconsiderate driver, but nowadays the well-mannered motorist is the exception to the rule. Perhaps the situation calls for a “ Be Kind to Other Drivers” campaign ; otherwise it may get completely out of hand. Road politeness is not good manners, but good sense too. It takes the most cool headed and good tempered of drivers to resist the temptation to revenge when subjected to uncivilized behavior. On the other hand, a little politeness goes a long way towards relieving the tensions of motoring. A friendly nod or a wave of acknowledgement in response to an act of politeness helps to create an atmosphere of goodwill and tolerance so necessary in modem traffic conditions. But such acknowledgements of politeness are all too rare today. Many drivers nowadays don’t even seem able to recognize politeness when they see it.

　　However, misplaced politeness can also be dangerous. Typical examples are the drive who brakes violently to allow a car to emerge from a side street at some hazard to following traffic, when a few seconds later the road would be clear anyway; or the man who waves a child across a zebra crossing into the path of oncoming vehicles that may be unable to stop in time. The same goes for encouraging old ladies to cross the road wherever and whenever they care to. A veteran driver, whose manners are faultless, told me it would help if motorists learnt to filter correctly into traffic streams one at a time without causing the total blockages that give rise to bad temper. Unfortunately, modem motorists can’t even learn to drive, let alone master the subtler aspects of roadsmanship. Years ago the experts warned us that the car ownership explosion would demand a lot more give and take from all road users. It is high time for all of us to take this message to heart.

　　56.In the author’s opinion，•

　　A.strict traffic regulations are badly needed

　　B.drivers should apply road politeness properly

　　C.rude drivers should be punished

　　D.drivers should avoid traffic jams

　　57.The sentence “You might tolerate the odd road hog …the rule” ( Para. 1) implies that

　　A.our society is unjust towards well-mannered motorists

　　B.rude drivers can be met only occasionally

　　C.the well-mannered motorist today cannot tolerate impolite drivers

　　D.nowadays impolite drivers constitute the majority of motorists

　　58.What would most probably happen nowadays when you show politeness to other drivers on road?

　　A.They would show politeness to you inversely.

　　B.They would show thankfulness to you.

　　C.They would just drive on as nothing has happened.

　　D.They would make way for you readily.

　　59.The examples in the third paragraph are used to illustrate.

　　A.it is polite for drivers to let children and the old to cross the road first

　　B.the politeness shown in the wrong moment can lead to dangers

　　C.it is dangerous to allow a car to emerge from a side street to follow traffic

　　D.drivers should recognize other’s politeness at the right moment

　　60.Experts have long pointed out that in the face of car ownership explosion，.

　　A.road users should make more sacrifice

　　B.drivers should be ready to yield to each other

　　C.drivers should have more communication among themselves

　　D.drivers will suffer a great loss if they pay no respect to others

　　Passage Three

　　Questions 61 to 65 are based on the following passage.

　　The phrase “progressive education” is one, if not protest, at least of contrast, of contrast, of contrast with an education which was predominantly static in subject-matter, authoritarian in methods, and mainly passive and receptive from the side of the young. But the philosophy of education must go beyond any idea of education that is formed by way of contrast, reaction and protest, for it is an attempt to discover what education is and how it takes place. Only when we identify education with schooling does it seem to be a simple thing to tell what education actually is, and yet a clear idea of what it is gives us our only criterion for judging and directing what goes on in schools. It is sometimes supposed that it is the business of the philosophy of education to tell what education should be. But the only way of deciding what education should be, at least, the only way which does not lead us into the clouds, is discovery of what education takes place when education really occurs.

　　And before we can formulate a philosophy of education we must know human nature is constituted in the concrete ; we must know about the working of actual social forces ; we must know about the operations through which basic raw materials are modified into something of greater value. The need for a philosophy of education is thus fundamentally the need for finding out what education really is. We have to take those cases in which we find there is a real development of desirable powers, and then find out how this development took place. Then we can project what has taken place in these instances as a guide for directing our other efforts. The need for this discovery and this projection is the need for a

　　philosophy of education.

　　What then is education when we find actual satisfactory specimens of it in existence? In the first place, it is a process of development, of growth. And it is the process and not merely the result that is important. A truly healthy person is not something fixed and completed. He is a person whose processes and activities go on in such a way that he will continue to be healthy. Similarly, an educated person is the person who has the power to go on and get more education. In any case, development and growth involve change, modification, and modification in definite directions. It is quite possible for a teacher, under the supposed sanction of the idea of cultivating individuality, to fixate a pupil more or less at his existing level. Respect for individuality is primarily intellectual. It signifies studying the individual to see what is there to work with. Having this sympathetic understanding, the practical work then begins, for the practical work is one of modification, of changing, of reconstruction continued without end. The change must at least be towards more effective techniques, towards greater self-reliance, towards a more thoughtful and inquiring disposition, one more capable of persistent effort in meeting obstacles.

　　61.According to the author, the philosophy of education.

　　A.is the same as the conception of progressive education

　　B.studies the essence of education and the way it occurs

　　C.conforms to any idea of education that is conservative and authoritarian

　　D.deals with the judgment and direction of school management

　　62.The philosophy of education is supposed to.

　　A.result from real understanding of occurrences in actual schooling

　　B.be the only way leading to obscure understanding of education

　　C.have taken place when education first came into existence

　　D.be the basis on which decisions on practical education are formulated

　　63.The chief task of the philosophy of education is to.

　　A.analyze the constitution of human nature in great detail

　　B.clarify the practical effects of social forces on education

　　C.present how raw materials are made into valuable goods

　　D.find out the ways of how to bring out the best human faculties

　　64.The significance of desirable education lies.

　　A.more in its operation than in its modification

　　B.less in its modification than in its operation

　　C.not only in its result but also in its process

　　D.rather in its process than in its result

　　65.What can we learn from the last paragraph?，

　　A.The supposed approval of the idea of cultivating individuality is reasonable

　　B.Modification refers to making a pupil develop in a fixed direction.

　　C.To respect individuality means to discover whether an individual is worth modifying

　　D.True education should be based on cultivating a student according to his/her natural talent.

　　Passage Four

　　Questions 66 to 70 are based on the following passage.

　　The Supreme Court’s decisions on physician-assisted suicide carry important implications for how medicine seeks to relieve dying patients of pain and suffering. Although it ruled that there is no constitutional right to physician-assisted suicide, the court in effect supported the medical principle of “ double effect”，a centuries-old moral principle holding that an action having two effects—a good one that is intended and a harmful one that is foreseen—is permissible if the actor intends only the good effect.

　　Doctors have used that principle in recent years to justify using high doses of morphine to control terminally ill patients’ pain, even though increasing dosages will eventually kill the patient. Nancy Dubler, director of Montefiore Medical Center, contends that the principle will shield doctors who “until now have very, very strongly insisted that they could not give patients sufficient medication to control their pain if that might hasten death”. George Annas, chair of the health law department at Boston University, maintains that, as long as good doctor prescribes a drug for a legitimate medical purpose, the doctor has done nothing illegal even if the patient uses the drug to hasten death. “It’s like surgery, he says. “We don’t call those deaths homicides because the doctors didn’t intend to kill their patients, although they risked their death. If you’re a physician, you can risk your patient’s suicide as long as you don’t intend their suicide. ”

　　On another level, many in the medical community acknowledge that the assisted-suicide debate has been fueled in part by the despair of patients for whom modem medicine has prolonged the physical agony of dying. Just three weeks before the Court’s ruling on physician-assisted suicide, the National Academy of Science (NAS) released a two-volume report, Approaching Death: Improving Care at the End of Life. It identifies the undertreatment of pain and the aggressive use of “ineffectual and forced medical procedures that may prolong and even dishonor the period of dying” as the twin problems of end-of-life care. The profession is taking steps to require young doctors to train in hospitals, to test knowledge of aggressive pain management therapies, to develop a Medicare billing code for hospital-based care, and to develop new standards for assessing and treating pain at the end of life. Annas says lawyers can play a key role in insisting that these well-meaning medical initiatives translate into better care. “A large number of physicians seem unconcerned with the pain their patients are needlessly and predictably suffering”，to the extent that it constitutes “systematic patient abuse”. He says medical licensing boards “ must make it clear that painful deaths are presumptively ones that are incompetently managed and should result in license suspension”.

　　66.We learn from the passage that•

　　A.doctors never increase drug dosages to control their patients’ pain

　　B.it is still illegal for doctors to help the dying end their lives

　　C.the Supreme Court strongly opposes physician-assisted suicide

　　D.patients have no constitutional right to commit suicide

　　67.George Annas may agree that.

　　A.a doctor’s medication shouldn’t be justified by his intentions

　　B.doctors cannot give patients large dosages of medication on any account

　　C.high-dosage pain-relieving medication can be prescribed

　　D.doctors should be held guilty if they risk their patients’ death

　　68.According to the NAS’s report, one of the problems in end-of-life care is.

　　A.prolonged medical procedures

　　B.inadequate treatment of pain

　　C.systematic drug abuse

　　D.insufficient hospital care

　　69.What’s the possible meaning of “ aggressive”( Line 3, Para. 7) ?

　　A.Bold.B. Harmful.C. Positive.D. Energetic.

　　70.According to George Annas，which of the following medical behaviors should be punished?

　　A.Treating patient impatiently.

　　B.Giving patients more medicine than needed.

　　C.Reducing drug dosages for patients.

　　D.Prolonging the needless suffering of the patients.

　　Passage Five

　　Questions 71 to 75 are based on the following passage.

　　Smell is the most direct of all the senses. It is thought to be the oldest sense in terms of human evolution, which may explain why smell is hard-wired into the brain. The olfactory nerve, which manages the perception of smells, is essentially an extension of the brain. The olfactory nerve provides a direct link from receptors at the top of the nose to the portion of the brain that controls memory, emotion, and behavior. The olfactory system detects certain airborne chemicals that enter the nose and then transmits this chemical information to the limbic system in the brain. The olfactory region at the upper end of each nostril is yellow, moist, and full of fatty substances. The shade of yellow indicates the strength of the

　　sense of smell: the deeper the shade, the keener and more acute it is. Animals have a very strong sense of smell, so their olfactory regions are dark yellow to reddish brown, while those of humans are light yellow.

　　When an odorous substance enters the nose, it binds to olfactory receptor cells, the neurons lining the yellow upper portion of the nasal cavity. Olfactory receptor cells contain microscopic hairs called cilia that extend into the layer of mucus coating the inside of the nose. Odor molecules diffuse into this region and are absorbed by the cilia of the olfactory receptor cells. What this means is that when we hold a rose to our nose and inhale, odor molecules float up into the nasal cavity, where they are absorbed by five million olfactory receptor cells. The receptor cells alert the olfactory nerve, which sends impulses to the brain’s olfactory bulb, or smell center. Thus, olfactory information about the rose enters the brain’s limbic system, where, in most of us, it stimulates a feeling of pleasure. The limbic system of the brain integrates memory, emotion, and behavior. The system is composed of a group of related nervous system structures that are the functional center of emotions such as anger, fear, pleasure, and sadness. The components of the limbic system are linked to the cerebral cortex, the part of the brain involved in complex learning, reasoning, and personality. The cerebral cortex makes decisions about the emotional content of these unique human qualities after “consulting” the limbic system and the other brain centers in processing and retrieving memories. It may, in turn, use memories to modify behavior.

　　Scent may be the strongest trigger of memory and emotions. When we inhale a scent，receptors in the brain’s limbic center compare the odor entering our nose to odors stored in our memory. Along the way, memories associated with those odors are stimulated. A smell can be overwhelmingly nostalgic because it triggers powerful images and emotions. The waxy fragrance of crayons can instantly transport us to our second-grade classroom, or the scent of freshly mown grass can flood us with the joy of summer freedom. What we see and hear may fade quickly in short-term memory, but what we smell is sent directly to long-term memory. Smells can increase alertness and stimulate learning and retention. In one study, children memorized a word list, which was presented both with and without accompanying scents. The children recalled words on the list more easily and with higher accuracy when the list was given with scents than without, showing the link between smell and the ability to retain information. In another study, researchers examined how various smells can increase alertness and decrease stress. They found that the scent of lavender could wake up the metabolism and make people more alert. They also found that the smell of spiced apples could reduce blood pressure and avert a panic attack in people under stress.

　　71.Why does the author use the term “hard-wired” in describing the sense of smell and the brain?

　　A.To describe the texture and feel of the olfactory nerve

　　B.To emphasize the close connection between smell and the brain

　　C.To compare the power of smell with that of other senses

　　D.To explain how the sense of smell evolves in early humans

　　72.Of what significance is the color of the olfactory region at the upper end of each nostril?

　　A.The color changes with different airborne chemicals.

　　B.The significance of the color is little understood.

　　C.The color becomes darker when an odor is present.

　　D.The color shows the strength of the ability to smell.

　　73.What happens when the cilia of the olfactory receptor cells absorb odor molecules?

　　A.The tiny hairs inside the nose become darker in color.

　　B.The nervous system activates the digestive system.

　　C.The olfactory nerve sends impulses to the brain.

　　D.Some receptor cells die and are replaced by new cells.

　　74.Why does the author mention “crayons” and “freshly mown grass” in Paragraph5?

　　A.To give examples of smells that can trigger memories and emotions

　　B.To compare typical responses to two common smells

　　C.To explain why smells are likely to affect person’s behavior

　　D.To identify smells that can increase alertness and work efficiency

　　75.What can be inferred from Paragraph 6 about learning?

　　A.Learning cannot take place unless all of the senses are stimulated.

　　B.Scents can strengthen the ability to hold new information in the memory.

　　C.It is easier to recall previous learning than it is to retain new information.

　　D.Children will not learn much if they are distracted by offensive odors.

　　Passage Six

　　Questions 76 to 80 are based on the following passage.

　　Bird migration is one of the most interesting yet least understood natural phenomena. Every fall birds from northern latitudes fly in groups to the warmer southern latitudes and then return north in the spring. Scientists agree on the main reasons for migration： to follow the food supply and to avoid harsh climate conditions. For example, insects disappear during the cold months, prompting insect-dependent birds to fly south to warm areas where insects breed. No similar consensus has emerged, however, about how birds are able to navigate. Despite many recent experiments, bird experts still do not know how birds arrive at the same destination every year and then find their way back home in the spring. Some have suggested that birds find their way by following landmarks, such as rivers and mountain ranges. Experiments have confirmed that some species do follow such topographic features. But that method cannot explain how some birds travel at night. Other studies show that some nocturnal birds navigate by the stars. But that explanation cannot explain daytime migration or travel when the skies are cloudy.

　　The most popular explanation currently is that birds are guided by Earth’s magnetic poles. The mechanism by which that works has not yet been proved. One theory points to the fact that some birds’ brains contain magnetite, a naturally occurring magnetic compound consisting of iron oxide. Magnetite has been found in many animals, including birds. With magnets embedded in their brains, birds would be able to sense the magnetic fields of the North and South Poles. A recent experiment with homing pigeons provided some evidence that magnetite does play a crucial role in migration. Homing pigeons are known to have the ability to return to their homes after being taken hundreds of miles away. Researchers found that they could train homing pigeons to recognize changes in a magnetic field. When a surrounding magnetic field was normal, the birds would gather at one end of a cage. But when the field’s polarity was altered, they hopped to the other end, suggesting that they were detecting and responding to changes in the magnetic field. Another theory has been offered to explain this sensitivity to magnetic poles, a theory that draws upon quantum mechanics, which is the study of how particles move inside an atom. It relies on the fact that electrons come in pairs that orbit the nucleus of an atom. The two electrons spin in opposite directions, creating two magnets that neutralize each other. But when molecules split and react with other molecules to form compounds, the electron pairs may no longer spin in opposite directions.

　　Instead, they may repel each other, as when two north ends of magnets are pressed together. The electrons struggle to change direction in order to achieve a stable state in which the two electrons again neutralize each other, giving off no magnetic field. The theory is that these disturbed electron pairs are created in birds when they are exposed to changes in light. The birds can sense the efforts of the electrons in trying to reach a condition of stability because of the slight changes in the pull of the North and South Poles. In this way, the birds can detect the direction of the poles while they are in flight.

　　In one experiment to confirm this effect，a group of European robins were tricked by artificial light to believe that it was time for spring migration. The birds became eager to fly north. The changes in light triggered the electron-pair movement described above，exposing the robins to the magnetic field accompanying the electron pairs. The birds became disoriented and flew in all directions. The simulated magnetic fields were much too weak to be detected by the birds’ natural magnetite, suggesting to the experimenters that the electron pairs, not the magnetite, were responsible for the birds’ confused flying. The current view, therefore, is that light plays an important role in guiding bird migration. This may be why birds turn their heads from side to side before flying off. Their eyes are collecting the surrounding light, which in turn allows them to process and analyze the existing magnetic fields and to keep themselves pointed in the right direction.

　　76.According to Paragraph 1, insects influence bird migration in which of the following ways?

　　A.Insects generate a magnetic field that birds can detect.

　　B.Insects provide a food supply that exists only in warm climates.

　　C.Birds follow the paths taken by flying insects.

　　D.Birds know when to migrate by a sudden increase in insect population.

　　77.According to Paragraph 3, birds can detect the magnetic fields of the North and South Poles because.

　　A.they sense the motion of electron pairs

　　B.they can locate the poles by following landmarks

　　C.they ingest metal particles that are attracted by the poles

　　D.they have magnetite in their brains

　　78.The author discusses homing pigeons in Paragraph 4 in order to.

　　A.provide an example of how humans can train birds

　　B.describe an experiment showing the importance of magnetite

　　C.show that homing pigeons return home by following landmarks

　　D.report homing pigeons，behavior inside a cage

　　79.According to the passage, all of the following are theories about how birds navigate except:

　　A.They follow landmarks like rivers and mountains.

　　B.They are guided by their position relative to the stars.

　　C.They feel vibrations in nerve endings in their brains.

　　D.They respond to changes in light.

　　80.According to the passage，the author mentions all of the following about electrons except:

　　A.Changes in light cause electron pairs to change the direction of their spin.

　　B.Magnetite contains electrons that repel each other.

　　C.Electrons that spin in opposite directions neutralize each other.

　　D.The nucleus of an atom is orbited by electron pairs.

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