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1、精 选 400句 托 福 阅 读 长 难 句 OG&BO第 一 类 1.The same thing happens to thisday,though on a smaller scale,wherever a sediment-laden river orstream emerges from a mountainvalley onto relatively flat land,dropping its load as the currentslows:the water usually spreadsout fanwise,depositing thesediment in the fo
2、rm of a smooth,fan-shaped slope.2.In lowland country almost any spot on theground may overlie what was once the bedof a river that has since become buried bysoil;if they are now below the waters uppersurface(the water table),the gravels andsands of the former riverbed,and itssandbars,will be saturat
3、ed withgroundwater.3.But note that porosity is not the same aspermeability,which measures the ease withwhich water can flow through a material;this depends on the sizes of the individualcavities and the crevices linking them.4.If the pores are large,the water in them willexist as drops too heavy for
4、 surface tensionto hold,and it will drain away;but if thepores are small enough,the water in themwill exist as thin films,too light to overcomethe force of surface tension holding them inplace;then the water will be firmly held.5.But the myths that have grown up aroundthe rites may continue as part
5、of the groupsoral tradition and may even come to beacted out under conditions divorced fromthese rites.6.Another,advanced in the twentieth century,suggests that humans have a gift for fantasy,through which they seek to reshape realityinto more satisfying forms than thoseencountered in daily life.7.F
6、or example,one sign of this condition is theappearance of the comic vision,sincecomedy requires sufficient detachment toview some deviations from social norms asridiculous rather than as serious threats tothe welfare of the entire group.8.Timberline trees are normally evergreens,suggesting that thes
7、e have some advantageover deciduous trees(those that lose theirleaves)in the extreme environments of theupper timberline.9.This is particularly true for trees in themiddle and upper latitudes,which tend toattain greater heights on ridges,whereas inthe tropics the trees reach their greaterheights in
8、the valleys.10.As the snow is deeper and lasts longer inthe valleys,trees tend to attain greaterheights on the ridges,even though they aremore exposed to high-velocity winds andpoor,thin soils there.11.Wind velocity also increases with altitudeand may cause serious stress for trees,as ismade evident
9、 by the deformed shapes athigh altitudes.12.Some scientists have proposed that thepresence of increasing levels of ultravioletlight with elevation may play a role,whilebrowsing and grazing animals like the ibexmay be another contributing factor.13.Probably the most importantenvironmental factor is t
10、emperature,for ifthe growing season is too short andtemperatures are too low,tree shoots andbuds cannot mature sufficiently to survivethe winter months.14.Immediately adjacent to the timberline,the tundra consists of a fairly completecover of low-lying shrubs,herbs,andgrasses,while higher up the num
11、ber anddiversity of species decrease until there ismuch bare ground with occasional mossesand lichens and some prostrate cushionplants.15.In order for the structure to achieve thesize and strength necessary to meet itspurpose,architecture employs methods ofsupport that,because they are based onphysi
12、cal laws,have changed little sincepeople first discovered them-even whilebuilding materials have changeddramatically.16.Some of the worlds finest stonearchitecture can be seen in the ruins of theancient Inca city of Machu Picchu high in theeastern Andes Mountains of Peru.17.It works in compression t
13、o divert theweight above it out to the sides,where theweight is borne by the vertical elements oneither side of the arch.18.The Ogallala aquifer is a sandstoneformation that underlies some 583,000square kilometers of land extending fromnorthwestern Texas to southern SouthDakota.19.Unfortunately,the
14、cost of water obtainedthrough any of these schemes wouldincrease pumping costs at least tenfold,making the cost of irrigated agriculturalproducts from the region uncompetitive onthe national and international markets.20.Whatever the final answer to the watercrisis may be,it is evident that within th
15、eHigh Plains,irrigation water will never againbe the abundant,inexpensive resource itwas during the agricultural boom years ofthe mid-twentieth century.21.To take an extreme example,farmlandsdominated by a single crop are so unstablethat one year of bad weather or the invasionof a single pest can de
16、stroy the entire crop.22.Ecologists are especially interested toknow what factors contribute to theresilience of communities because climaxcommunities all over the world are beingseverely damaged or destroyed by humanactivities.23.The destruction caused by the volcanicexplosion of Mount St.Helens,in
17、 thenorthwestern United States,for example,pales in comparison to the destructioncaused by humans.24.Many ecologists now think that therelative long-term stability of climaxcommunities comes not from diversity butfrom the patchiness“of the environment,an environment that varies from place toplace su
18、pports more kinds of organismsthan an environment that is uniform.25.Similarly,a plant or animal cannotsquander all its energy on growing a bigbody if none would be left over forreproduction,for this is the surest way toextinction.26.At the other extreme are competitors/almost all of whose resources
19、 are investedin building a huge body,with a bareminimum allocated to reproduction.27.A new plant will spring up wherever aseed falls on a suitable soil surface,butbecause they do not build big bodies,theycannot compete with other plants for space,water,or sunlight.28.These plants are termed opportun
20、istsbecause they rely on their seeds falling intosettings where competing plants have beenremoved by natural processes,such asalong an eroding riverbank,on landslips,orwhere a tree falls and creates a gap in theforest canopy.29.Human landscapes of lawns,fields,orflowerbeds provide settings with bare
21、 soiland a lack of competitors that are perfecthabitats for colonization by opportunists.30.A massive oak claims its ground for 200years or more,outcompeting all otherwould-be canopy trees by casting a denseshade and drawing up any free water in thesoil.31.It should be noted,however,that thepure opp
22、ortunist or pure competitor is rarein nature,as most species fall between theextremes of a continuum,exhibiting a blendof some opportunistic and some competitivecharacteristics.32.Because some paintings were madedirectly over others,obliterating them,it isprobable that a paintings value ended withth
23、e migration it pictured.33.One Lascaux narrative picture,whichshows a man with a birdlike head and awounded animal,would seem to lendcredence to this third opinion,but there isstill much that remains unexplained.34.Perhaps so much time has passed thatthere will never be satisfactory answers tothe ca
24、ve images,but their mystique onlyadds to their importance.35.In 1994 there were nearly 20,000 windturbines worldwide,most grouped inclusters called wind farms that collectivelyproduced 3,000 megawatts of electricity.36.Most were in Denmark(which got 3percent of its electricity from wind turbines)and
25、 California(where 17,000 machinesproduced 1 percent of the states electricity,enough to meet the residential needs of acity as large as San Francisco).37.In the long run,electricity from large windfarms in remote areas might be used tomake hydrogen gas from water duringperiods when there is less tha
26、n peakdemand for electricity.38.Large wind farms might also interferewith the flight patterns of migratory birds incertain areas,and they have killed largebirds of prey(especially hawks,falcons,andeagles)that prefer to hunt along the sameridge lines that are ideal for wind turbines.39.David Douglas,
27、Scottish botanicalexplorer of the 1830s,found a disturbingchange in the animal life around the fortduring the period between his first visit in1825 and his final contact with the fort in1832.40.The researchers Peter Ucko and AndreeRosenfeld identified three principal locationsof paintings in the cav
28、es of western Europe:(1)in obviously inhabited rock shelters andcave entrances;(2)in galleries immediatelyoff the inhabited areas of caves;and(3)inthe inner reaches of caves,whose difficultyof access has been interpreted by some as asign that magical-religious activities wereperformed there.41.Perha
29、ps,like many contemporarypeoples,Upper Paleolithic men and womenbelieved that the drawing of a human imagecould cause death or injury,and if that wereindeed their belief,it might explain whyhuman figures are rarely depicted in caveart.42.For example,wild cattle(bovines)andhorses are portrayed more o
30、ften than wewould expect by chance,probably becausethey were larger and heavier(meatier)thanother animals in the environment.43.Consistent with this idea,according to theinvestigators,is the fact that the art of thecultural period that followed the UpperPaleolithic also seems to reflect how peoplego
31、t their food.44.But in that period,when getting food nolonger depended on hunting large gameanimals(because they were becomingextinct),the art ceased to focus onportrayals of animals.45.When the well reaches a pool,oil usuallyrises up the well because of its densitydifference with water beneath it o
32、r becauseof the pressure of expanding gas trappedabove it.46.More than one-quarter of the worlds oiland almost one-fifth of the worlds naturalgas come from offshore,even thoughoffshore drilling is six to seven times moreexpensive than drilling on land.47.While there are a dozen or more massextinctio
33、ns in the geological record,theCretaceous mass extinction has alwaysintrigued paleontologists because it marksthe end of the age of the dinosaurs.48.The explosion lifted about 100 trillion tonsof dust into the atmosphere,as can bedetermined by measuring the thickness ofthe sediment layer formed when
34、 this dustsettled to the surface.49.Such a quantity of material would haveblocked the sunlight completely fromreaching the surface,plunging Earth into aperiod of cold and darkness that lasted atleast several months.50.The explosion is also calculated to haveproduced vast quantities of nitric acid an
35、dmelted rock that sprayed out over much ofEarth,starting widespread fires that musthave consumed most terrestrial forests andgrassland.51.Following each mass extinction,there is asudden evolutionary burst as new speciesdevelop to fill the ecological niches openedby the event.52.Earth is a target in
36、a cosmic shootinggallery,subject to random violent eventsthat were unsuspected a few decades ago.53.Early in the century,a pump had comeinto use in which expanding steam raised apiston in a cylinder,and atmosphericpressure brought it down again when thesteam condensed inside the cylinder to forma va
37、cuum.54.The final step came when steam wasintroduced into the cylinder to drive thepiston backward as well as forward therebyincreasing the speed of the engine andcutting its fuel consumption.55.Iron manufacturers which had starved forfuel while depending on charcoal alsobenefited from ever-increasi
38、ng supplies ofcoal;blast furnaces with steam-poweredbellows turned out more iron and steel forthe new machinery.56.He received rudimentary village schoolingbut mostly he roamed his uncles farmcollecting the fossils that were so abundantin the rocks of the Cotswold hills.57.The companies building the
39、 canals totransport coal needed surveyors to helpthem find the coal deposits worth mining aswell as to determine the best courses for thecanals.58.In 1831 when Smith was finallyrecognized by the Geological Society ofLondon as the father of English geology”,itwas not only for his maps but also forsom
40、ething even more important.59.Maturation of the frontal lobes of thebrain continues throughout early childhood,and this part of the brain may be critical forremembering particular episodes in waysthat can be retrieved later.60.Demonstrations of infants and toddlerslong-term memory have involved thei
41、rrepeating motor activities that they hadseen or done earlier,such as reaching in thedark for objects,putting a bottle in a dollsmouth,or pulling apart two pieces of a toy.61.Through hearing stories with a clearbeginning,middle,and ending children maylearn to extract the gist of events in waysthat t
42、hey will be able to describe many yearslater.62.The world looks very different to a personwhose head is only two or three feet abovethe ground than to one whose head is five orsix feet above it,Older children and adultsoften try to retrieve the names of thingsthey saw,but infants would not haveencod
43、ed the information verbally.63.General knowledge of categories ofevents such as a birthday party or a visit tothe doctors office helps older individualsencode their experiences,but again,infantsand toddlers are unlikely to encode manyexperiences within such knowledgestructures.64.Physiological immat
44、urity may be part ofwhy infants and toddlers do not formextremely enduring memories,even whenthey hear stories that promote suchremembering in preschoolers.65.In 1947 Norwegian adventurer ThorHeyerdahl drifted on a balsa-log raftwestward with the winds and currentsacross the Pacific from South Ameri
45、ca toprove his theory that Pacific islanders wereNative Americans(also called AmericanIndians).66.Contrary to the arguments of some thatmuch of the pacific was settled byPolynesians accidentally marooned afterbeing lost and adrift,it seems reasonablethat this feat was accomplished bydeliberate colon
46、ization expeditions that setout fully stocked with food anddomesticated plants and animals.67.The undisputed pre-Columbian presencein Oceania of the sweet potato,which is aNew World domesticate,has sometimesbeen used to support HeyerdahlsAmerican Indians in the Pacific“theories.68.As Patrick Kirch,a
47、n Americananthropologist,points out,rather thanbeing brought by rafting South Americans,sweet potatoes might just have easily beenbrought back by returning Polynesiannavigators who could have reached the westcoast of South America.69.Conditions that promote fossilization ofsoft-bodied animals includ
48、e very rapidcovering by sediments that create anenvironment that discouragesdecomposition.70.This 700-million-year-old formation givesfew clues to the origins of modern animals,however,because paleontologists believe itrepresents an evolutionary experiment thatfailed.71.At one time,the animals prese
49、nt in thesefossil beds were assigned to various modernanimal groups,but most paleontologistsnow agree that all Tommotian fossilsrepresent unique body forms that arose inthe early Cambrian period and disappearedbefore the end of the period,leaving nodescendants in modern animal groups.72.These fossil
50、 beds provide evidence ofabout 32 modern animal groups,plus about20 other animal body forms that are sodifferent from any modern animals that theycannot be assigned to any one of themodern groups.73.With question such as these clearly beforethem,the scientists aboard the GlomarChallenger processed t