单选题In most earthquakes the Earth's crust cracks like porcelain. Stress builds up until a fracture forms at the depth of a few kilometers and the crust slips to relieve the stress. Some earthquakes, however, take place hundreds of kilometers down in the Earth's mantle, where high pressure makes rock so ductile that it flows instead of cracking, even under stress severe enough to deform it like putty. How can there be earthquakes at such depths? That such deep events do occur has been accepted only since 1927, when the seismologist Kiyoo Wadati convincingly demonstrated their existence. Instead of comparing the arrival times of seismic waves at different locations, as earlier researchers had done, Wadati relied on a time difference between the arrival of primary(P)waves and the slower secondary(S)waves. Because P and S waves travel at different but fairly constant speeds; the interval between their arrivals increases in proportion to the distance from the earthquake focus, or a rupture point. For most earthquakes, Wadati discovered, the interval was quite short near the epicenter, the point on the surface where shaking is the strongest. For a few events, however, the delay was long enough at the epicenter. Wadati saw a similar pattern when he analyzed data on the intensity of shaking. Most earthquakes had a small area of intense shaking, which weakened rapidly with increasing distance from the epicenter, but others were characterized by a lower peak intensity, felt over a broader area. Both the P-S intervals and the intensity patterns suggested two kinds of earthquakes: the more common shallow events, in which the focus lay just under the epicenter, and the deep events, with a focus several hundred kilometers down. The question remained: how can such quakes occur, given that mantle rock at a depth of more than 50 kilometers is too flexible to store enough stress to fracture? Wadati's work suggested that deep events occur in areas(now called Wadati-Benioff zones)where one crustal plate is forced under another and descends into the mantle. The descending rock is substantially cooler than the surrounding mantle and hence is less ductile and much more liable to fracture.

单选题Should the death penalty be ______ ?

单选题The patient who takes interest in everything and everybody is a formidable adversary for disease.

单选题In spite of " endless talk of difference" , American society is an amazing machine for homogenizing people. There is " the democratizing uniformity of dress and discourse, and the casualness and absence of deference" characteristic of popular culture. People are absorbed into "a culture of consumption" launched by the 19th century department stores that offered "vast arrays of goods in an elegant atmosphere. Instead of intimate shops catering to a knowledgeable elite," these were stores "anyone could enter, regardless of class or background. This turned shopping into a public and democratic act. " The mass media, advertising and sports are other forces for homogenization. Immigrants are quickly fitting into this common culture, which may not be altogether elevating but is hardly poisonous. Writing for the National Immigration Forum, Gregory Rodriguez reports that today's immigration is neither at unprecedented levels nor resistant to assimilation. In 1998 immigrants were 9. 8 percent of population; in 1900, 13. 6 percent . In the 10 years prior to 1990, 3. 1 immigrants arrived for every 1, 000 residents; in the 10 years prior to 1890, 9. 2 for every 1, 000. Now, consider three indices of assimilation — language, home ownership and intermarriage. The 1990 Census revealed that " a majority of immigrants from each of the fifteen most common countries of origin spoke English "well" or "very well" after ten years of residence. " The children of immigrants tend to be bilingual and proficient in English. " By the third generation, the original language is lost in the majority of immigrant families. " Hence the description of America as a "graveyard" for languages. By 1996 foreign-born immigrants who had arrived before 1970 had a homeownership rate of 75. 6 percent, higher than the 69. 8 percent rate among native-born Americans. Foreign-born Asians and Hispanics " have higher rates of intermarriage than do U. S born whites and blacks. " By the third generation, one third of Hispanic women are married to non-Hispanics, and 41 percent of Asian-American women are married to non-Asians. Rodriguez notes that children in remote villages around the world are fans of superstars like Arnold Schwarzenegger and Garth Brooks, yet " some Americans fear that immigrant living within the United States remain somehow immune to the nation's assimilative power. " Are there divisive issues and pockets of seething anger in America? Indeed. It is big enough to have a bit of everything. But particularly when viewed against America's turbulent past, today's social induces hardly suggest a dark and deteriorating social environment.

单选题The local people could hardly think of any good way to ______ poverty they had endured.

单选题Floods have undermined the foundation of the ancient bridge.

单选题The private life of having each individual make his or her own choice of beliefs and interest______.without the overarching public world of the state, which sustains a structure of Iaw appropriate to a self-determining association. A. is not possible B. would not be possible C. will not be possible D. by which

单选题Beijing's private cars will be banned from the roads______for one day a week during a six-month trial period.

单选题There were not personal goals.no desire to get ahead or to leave something behind. There were only God's decrees to be faithfully carried out

单选题Their request was ______ and consequently rejected.

单选题The actress was very______ at the insulting question raised by her opponent at the conference.(2007年清华大学考博试题)

单选题{{B}}PartB{{/B}}Thepassagebelowsummarizesthemainpointsofthepassage.Readthesummaryandthenselectthebestwordorphrasefromtheboxblow,accordingtothepassage.YoushoulddecideonthebestchoiceandmarkthecorrespondingletterontheAnswerSheetwithasinglelinethroughthecenter.Everymorning,Alliewakesupandaccompaniesherfriendtothewashroom.Sheturnsonthelight,soapsupawashcloth,andbeginscleaningherfriend'sface.IsAnieanextremelydevotedcompanion?Yes!Allieisacapuchinmonkeywhohelpsherdisabledfriendperformeverydaytasks.MonkeyslikeAlliearejustoneofmanykindsofanimalsthathelpimprove--orevensave--humanlives.Butnotallanimalsaresuitedtodoeveryjob.Certainanimalsare"hired"forspecificjobsbasedontheirtraits,orcharacteristics.Byusingdifferentmethodsofconditioning(traininganimalstoactinaparticularwayinresponsetoastimulus,orsignal),humanscanteachanimalstoperformextraordinarytasks.Throughouthistory,humanshavereliedonanimals'traitstogetcertainjobsdone.Forexample,comparedwithhumans,dogsare"farsuperiorattrackingdownodors",saysMarianBailey,ananimalbehavioristatHendersonStateUniversityinArkansas.That'sbecausedogshavemillionofolfactoryreceptors,orsmellnerves,intheirnoses.Forthatreason,huntersuseddogstotrackdownpreyeveninancientEgypt.Today,dogsmybeemployedtosniffoutillegalsubstancesinschoollockersorearthquakevictimsburiedbeneaththerabbleofthecollapsedbuildingorhighway.Primatesmaynotbegoodsinffers,buttheycancertainlylendahelpinghand--ortwo.Monkeysareperfecthelpmatesforquadriplegics,peopleparalyzedfromtheneckdownwhoareunabletousetheirownhands(andlegs).Likehumans,explainsBaileymonkeyshaveopposablethumbs--thumbsthatfacethehand'sotherfingers--somonkeyscanpickupobjects.Capuchinslearntoopendoors,cleanupspills,andunscrewbottletops.TheycanevengetasandwichoutoftherefrigeratorandloadyourfavoritetapeintotheVCR.AndspeakingofVCRs,animalsareevenhelpingscientistsmakeavideotape.JenniferHurley,ananimalresearcherattheLongMarineLabinSantaCruz,California,istrainingtwosealionstocarryvideocamerasontheirbackstorecordthenaturalbehaviorofwhales.Sohowdoyougetananimalemployeetodoitsjob?Theanswer,career-training.Trainersteachtheanimalstoobeytheirinstructionsthroughaprocesscalledconditioning.Mosttrainersconditionanimalsbyusingpositivereinforcement,rewardingananimalfordoingsomethingcorrectly,saysanimalbehavioristBailey.Forexample,trainersteachtheirdogshowtosniffoutdrugsbyhidingatowelwiththesmellofdrags."Dogslovetoretrieveobjectssothetowelbecomesareward",saysMorrisBerkowitz,whoheadsupacaninedrug-sniffingprograminNewYork.Afterrepeatingthisgameofhide-and-seekmanytimes,thedogbeginsto"associatetheodorwithareward",saysBerkowitz.Whenhegivesthecommand,orstimulus,thedogseekscotdrags(it'slikelearningtostudyhardforatestsinordertogetagoodgradeasareward.)At"HelpingHands--MonkeyHelpersfortheDisabled",capuchinmonkeysaretrainedtwicebeforebeingteamedwithadisabledhuman.First,monkeysareplacedwithafosterfamilytobecomesocializedtopeople.Forfiveyears,familieshelpthemonkeysadapttoahumanenvironment,sothemonkeyswilltrustandenjoybeingaroundpeople.Takingthemonkeysinwhenthey'refourtosixweeksoldisimportant,saysBailey."That'swhenmonkeysnormallybecomesocializedtoothermonkeys,"shesays.Second,trainersatHelpingHandstrainthemonkeystoperformspecifictaskstoassistaparticularperson.Forexample,amonkeymaybetrainedtoscratchanitch,orslipafloppydiscintoacomputerdive.Trainersrewardthemonkeysbyusingpositivereinforcement,suchasfood,drinks.Allieisacapuchin{{U}}16{{/U}}whohelpsherdisabledfriendperformeverydaytasks.Allieisa(n){{U}}17{{/U}}ofmanyanimalswhocanbe{{U}}18{{/U}}todocertainjobs.Besidesmonkeys,{{U}}19{{/U}}andsealionscanalsogivepeopleahelping{{U}}20{{/U}}.Dogsaregoodat{{U}}21{{/U}}downpreyandsniffingout{{U}}22{{/U}}and{{U}}23{{/U}}becausetheyhavemillionsof{{U}}24{{/U}}intheirnoseMonkeysaregoodhelperforthe{{U}}25{{/U}},whocannotlookafterthemselves.Sealionscanhelpscientiststorecordthe{{U}}26{{/U}}ofwhalesbecausethey:can{{U}}27{{/U}}tothedeepocean.Inaddition,{{U}}28{{/U}}arepartofwhales'naturalenvironment,whichmakesthevideomore{{U}}29{{/U}}.Butanimalscannotdothejobs{{U}}30{{/U}}training.Themainprocessoftrainingiscalled{{U}}31{{/U}},whichuses{{U}}32{{/U}}.Duringthetraining,trainers{{U}}33{{/U}}ananimalfordoingsomething{{U}}34{{/U}}.Formonkeys,thepositivereinforcementcan{{U}}35{{/U}}ayearbeforetheyarequalifiedfortheirjobs.

单选题It"s often hard to see your mistakes as you"re making them. When it comes to living arrangements, a humdinger is being made in this country right now and few have noticed it yet. "Yikes!The kids are moving back in!" Thus goes the mantra of the baby boom generation, circa 2007. Analysts estimate that some 18 million adults between the ages of 20 and 34 live with their parents. That"s roughly a third of that age group. But letting the kids move back in is not the societal error we"re talking about. Instead, the big mistake is the loudly voiced chagrin of the boomers. Most mistakenly decry the notion of the boomerang generation. In order to fully appreciate the depth of the error being made here, we all need to step back a bit and look at the bigger picture. This epidemic of kids moving back home is first, not "unprecedented," and second, it"s not a bad thing. The precedent for this trend can be found among the other 6.2 billion non-Americans on the planet, many of whom happily live with their adult children, often in three-generation households. Then there"s the growing number of non-Anglo Americans, including many recent immigrants, who see no problem in having adult kids contribute to the household. Finally, the agrarian history of this country before World War II allowed kids to live and work around the farm weI1 into adulthood. Adult kids moving back home is merely the most noticeable symptom of a larger, fundamental transformation of American society. We are nationally beginning to recognize the costs of the independence the so-called greatest generation foisted on us. We can"t blame them. They did have to grow up fast. Kids in their generation went off to World War II and grew up on the bloody beaches of distant lands. After the war, the survivors had factories to build and the wealth to buy their white-picket-fence dream out West. They designed a social and fiscal system that has served their retirement years very well. But their historically unique retirement system mistakenly celebrated independence and ignored the natural state of human beings--that is, interdependence. Moreover, their system breaks down with the onslaught of their kids" retirement. We can already see the pension systems, both private and public, beginning to disintegrate under the weight of the baby boomers. We are now just starting to understand the substantial fiscal and psychological costs of separating the generations into so-called single-family homes with the ideal of a mother, father and two kids. But times change and so do cultures. Regarding boomerang kids, most demographers focus on the immediate explanations for the changes, such as the growing immigrant population, housing shortages and high prices, and out-of-wedlock childbearing. Many psychologists have noted that baby-boomer parents enjoy closer relationships with their fewer children that allow extended cohabitation. A recent survey conducted for Del Webb (a division of Pulte Homes Inc.)reports that only about one-quarter of baby boomers are happier once the kids move out. However, all these explanations are simply symptoms of the larger, more fundamental reuniting of Americans into households that include extended families--adult, kids, grandparents, grandchildren and other relatives -- rather than just nuclear families. The rate at which our American culture is adapting will accelerate as baby boomers begin retiring in waves. Creative housing arrangements are necessitating and allowing three generations to live together again- under one roof or in close proximity. Now some 6 million American grandparents are living under one roof with their grandchildren. Whether grandparents live in accessory apartments on the property or houses next door, these flexible housing options provide privacy and companionship at the same time. Grandparents can interact with their grandchildren while the parents work, and all benefit from the new togetherness. These 21st century housing arrangements are a creative way to handle the financial needs of the generation that is retiring and, yes, the adult children who are coming home. Such multigenerational households don"t make sense for everyone. Personality conflicts or family characteristics preclude such arrangements for some. Legal constraints such as building and zoning codes are formidable obstacles in most communities across the country. Often more room is mandated for parking your car than parking your grandmother. Home builders have been more interested in selling houses that satisfy immediate needs rather than anticipating the needs of the growing numbers of aging Americans. The culture itself frequently gets in the way, reinforcing the perception of a stigma attaching to lack of independence- the adult child who just won"t move out (and grow up) or the aging grandparent who eschews "being a burden". Despite these problems, once you begin talking with your friends about three-generation households, you will begin hearing stories about how such obstacles are being overcome. You also will begin hearing stories about the wonderful benefits of thinking about housing and family arrangements in creative ways. And you"ll hear stories about the fundamental satisfaction of living together again.

单选题Management was not acting in good faith when it alleged that worker's wages would have to be cut for the company to remain solvent.

单选题Against the wishes of many smaller countries, Europe is______ a stable, if undesirable, situation lacking any coherent policy of transnational coordination in basic and strategic research--despite the European Commission. A. tightened with B. put fast into C. stuck fast in D. fastened with

单选题Hardly a week passed ______ he got another new idea. A. that B. for C. but that D. but for

单选题Horseback riding ______ both the skill of handling a horse and the mastery of diverse riding styles.(2004年中国科学院考博试题)

单选题He hasn't analyzed why he tips so generously, but I think the proclivity stems from his high school years, when he worked as a busboy.