【单选题】Most of North America receives （） some form of continuous plant cover except in the arid and semiarid Southwest.
A. moisture to sustain sufficient
B. sufficient moisture to sustain
C. to sustain sufficient moisture
D. sufficient to sustain moisture
A. moisture to sustain sufficient
B. sufficient moisture to sustain
C. to sustain sufficient moisture
D. sufficient to sustain moisture
【单选题】thE unitED stAtEs soCiAl sECurity ACt, EnACtED in 1935, ContAinED thrEE mAjor progrAms A rEtirEmEnt FunD, unEmploymEntinsurAnCE, AnD wElFArE grAnts For loCAl DistriButE
【分析解答题】LISTENING 2类型：Lecture话题：Natural science详细内容：说Obsidian是从火山喷发之后一系列活动形成的一个东西，可以做成tools因为它尖锐，之后说了解obsidian的来源就能determine trade between两个地方(中间提了一个叫做B的地方)然后obsidian和火山能对应上，就像侦探查指纹一样，科学家用一个叫XFR的仪器(有题问好处)，一个是防止sample被破坏，另一个就听见一个词export，结果发现obsidian不是这个岛上的。
【单选题】rEADing 4 "Four stAgEs oF plAnEtAryDEvElopmEnt"
plAnEtAryDEvElopmEnt
→ in our stuDy oF thE plAnEtEArth, wE will FinD A Four-stAgE history oF plAnEtAry DEvElopmEnt. thE moon AnD All thE tErrEstriAl plAnEts hAvE pAssED through thEsE stAgEs, Although DiFFErEnCEs in thE wAy thE plAnEts wErE AltErED By thEsE stAgEs hAvE proDuCED DrAmAtiCAlly DiFFErEnt worlDs. thE moon, For ExAmplE, is muCh likEEArth, But its Evolution hAs BEEn DrAmAtiCAlly AltErED By its smAllEr sizE.As wE ExplorE thE solAr systEm, wE will DisCovEr not EntirEly nEw proCEssEs But rAthEr FAmiliAr EFFECts working in slightly DiFFErEnt wAys.
thE Four stAgEs
thE First stAgE oF plAnEtAry Evolution is DiFFErEntiAtion, thE sEpArAtion oF mAtEriAl ACCorDing to DEnsity.EArth now hAs A DEnsE CorE AnD A lowEr-DEnsity Crust, AnD thAt struCturE must hAvE originAtED vEry EArly.
DiFFErEntiAtion woulD hAvE oCCurrED EAsily iFEArth wErE moltEn whEn it wAs young. two sourCEs oF hEAt CoulD hAvE hEAtEDEArth. First, hEAt oF FormAtion woulD BE CrEAtED By in-FAlling mAtEriAl.A、mEtEoritE hittingEArth At high vEloCity ConvErts most oF its EnErgy oF motion into hEAt, AnD thE in-FAlling oF A lArgE numBEr oF mEtEoritEs CoulD rElEAsE trEmEnDous hEAt. iFEArth FormED rApiDly, this hEAt woulD hAvE ACCumulAtED muCh morE rApiDly thAn it CoulD lEAk AwAy, AnDEArth mAy hAvE BEEn moltEn whEn it FormED、A、sEConD sourCE oF hEAt rEquirEs morE timE to DEvElop. thE DECAy oF rADioACtivE ElEmEnts trAppED in thEEArth rElEAsEs hEAt grADuAlly; But, As soon AsEArth FormED, thAt hEAt woulD hAvE BEgun to ACCumulAtE AnD CoulD hAvE hElpED mEltEArth to FACilitAtE DiFFErEntiAtion. most oFEArth’s rADioACtivE ElEmEnts ArE now ConCEntrAtED in thE Crust, whErE thEy ContinuE to wArm AnD soFtEn thE roCk lAyErs.
EArth FormED By mAtEriAl FAlling togEthEr, But mEtEoritEs CoulD hAvE lEFt no trACE until A Crust soliDiFiED、onCEEArth hAD A hArD surFACE, thE mEtEoritEs CoulD Form CrAtErs. this sEConD stAgE in plAnEtAry Evolution, CrAtEring, wAs violEnt. thE hEAvy BomBArDmEnt wAs intEnsE BECAusE thE solAr nEBulA wAs FillED with roCky AnD iCy DEBris, AnD thE youngEArth wAs BAttErED By mEtEoritEs thAt pulvErizED thE nEwly Forming Crust. thE lArgEst mEtEoritEs BlAstED out CrAtEr BAsins hunDrEDs oF kilomEtErs in DiAmEtEr.As thE solAr nEBulA ClEArED, thE Amount oF DEBris DECrEAsED, AnD thE lEvEl oF CrAtEring FEll to its prEsEnt low lEvEl.Although mEtEoritEs still oCCAsionAlly strikEEArth AnD Dig CrAtErs, CrAtEring is no longEr thE DominAnt inFluEnCE onEArth’s gEology.As wE CompArE othEr worlDs withEArth, wE will DisCovEr trACEs oF this intEnsE pErioD oF CrAtEring, thE hEAvy BomBArDmEnt, on EvEry olD surFACE in thE solAr systEm.
→ thE thirD stAgE, FlooDing, no DouBt BEgAn whilE CrAtEring wAs still intEnsE. thE FrACturing oF thE Crust AnD thE hEAting CAusED By rADioACtivE DECAy AllowED moltEn roCk just BElow thE Crust to wEll up through FissurEs AnD FlooD thE DEEpEr BAsins. wE will DisCuss suCh FlooDED BAsins on othEr worlDs, suCh As thE moon, But All trACEs oF this EArly lAvA FlooDing hAvE BEEn DEstroyED By lAtEr gEologiCAl ACtivity inEArth’s Crust. onEArth, FlooDing ContinuED As thE AtmosphErE CoolED AnD wAtEr FEll As rAin, Filling thE DEEpEst BAsins to proDuCE thE First oCEAns.
![]()
notiCE thAt onEArth FlooDing involvEs Both lAvA AnD wAtEr, A CirCumstAnCE thAt wE will not FinD on most worlDs.
![]()
thE Fourth stAgE, slow surFACE Evolution, hAs ContinuED For thE lAst 3.5 Billion yEArs or morE.
![]()
EArth’s surFACE is ConstAntly ChAnging As sECtions oF Crust sliDE ovEr EACh othEr, push up mountAins, AnD shiFt ContinEnts.
![]()
Almost All trACEs oF thE Firs
plAnEtAryDEvElopmEnt
→ in our stuDy oF thE plAnEtEArth, wE will FinD A Four-stAgE history oF plAnEtAry DEvElopmEnt. thE moon AnD All thE tErrEstriAl plAnEts hAvE pAssED through thEsE stAgEs, Although DiFFErEnCEs in thE wAy thE plAnEts wErE AltErED By thEsE stAgEs hAvE proDuCED DrAmAtiCAlly DiFFErEnt worlDs. thE moon, For ExAmplE, is muCh likEEArth, But its Evolution hAs BEEn DrAmAtiCAlly AltErED By its smAllEr sizE.As wE ExplorE thE solAr systEm, wE will DisCovEr not EntirEly nEw proCEssEs But rAthEr FAmiliAr EFFECts working in slightly DiFFErEnt wAys.
thE Four stAgEs
thE First stAgE oF plAnEtAry Evolution is DiFFErEntiAtion, thE sEpArAtion oF mAtEriAl ACCorDing to DEnsity.EArth now hAs A DEnsE CorE AnD A lowEr-DEnsity Crust, AnD thAt struCturE must hAvE originAtED vEry EArly.
DiFFErEntiAtion woulD hAvE oCCurrED EAsily iFEArth wErE moltEn whEn it wAs young. two sourCEs oF hEAt CoulD hAvE hEAtEDEArth. First, hEAt oF FormAtion woulD BE CrEAtED By in-FAlling mAtEriAl.A、mEtEoritE hittingEArth At high vEloCity ConvErts most oF its EnErgy oF motion into hEAt, AnD thE in-FAlling oF A lArgE numBEr oF mEtEoritEs CoulD rElEAsE trEmEnDous hEAt. iFEArth FormED rApiDly, this hEAt woulD hAvE ACCumulAtED muCh morE rApiDly thAn it CoulD lEAk AwAy, AnDEArth mAy hAvE BEEn moltEn whEn it FormED、A、sEConD sourCE oF hEAt rEquirEs morE timE to DEvElop. thE DECAy oF rADioACtivE ElEmEnts trAppED in thEEArth rElEAsEs hEAt grADuAlly; But, As soon AsEArth FormED, thAt hEAt woulD hAvE BEgun to ACCumulAtE AnD CoulD hAvE hElpED mEltEArth to FACilitAtE DiFFErEntiAtion. most oFEArth’s rADioACtivE ElEmEnts ArE now ConCEntrAtED in thE Crust, whErE thEy ContinuE to wArm AnD soFtEn thE roCk lAyErs.
EArth FormED By mAtEriAl FAlling togEthEr, But mEtEoritEs CoulD hAvE lEFt no trACE until A Crust soliDiFiED、onCEEArth hAD A hArD surFACE, thE mEtEoritEs CoulD Form CrAtErs. this sEConD stAgE in plAnEtAry Evolution, CrAtEring, wAs violEnt. thE hEAvy BomBArDmEnt wAs intEnsE BECAusE thE solAr nEBulA wAs FillED with roCky AnD iCy DEBris, AnD thE youngEArth wAs BAttErED By mEtEoritEs thAt pulvErizED thE nEwly Forming Crust. thE lArgEst mEtEoritEs BlAstED out CrAtEr BAsins hunDrEDs oF kilomEtErs in DiAmEtEr.As thE solAr nEBulA ClEArED, thE Amount oF DEBris DECrEAsED, AnD thE lEvEl oF CrAtEring FEll to its prEsEnt low lEvEl.Although mEtEoritEs still oCCAsionAlly strikEEArth AnD Dig CrAtErs, CrAtEring is no longEr thE DominAnt inFluEnCE onEArth’s gEology.As wE CompArE othEr worlDs withEArth, wE will DisCovEr trACEs oF this intEnsE pErioD oF CrAtEring, thE hEAvy BomBArDmEnt, on EvEry olD surFACE in thE solAr systEm.
→ thE thirD stAgE, FlooDing, no DouBt BEgAn whilE CrAtEring wAs still intEnsE. thE FrACturing oF thE Crust AnD thE hEAting CAusED By rADioACtivE DECAy AllowED moltEn roCk just BElow thE Crust to wEll up through FissurEs AnD FlooD thE DEEpEr BAsins. wE will DisCuss suCh FlooDED BAsins on othEr worlDs, suCh As thE moon, But All trACEs oF this EArly lAvA FlooDing hAvE BEEn DEstroyED By lAtEr gEologiCAl ACtivity inEArth’s Crust. onEArth, FlooDing ContinuED As thE AtmosphErE CoolED AnD wAtEr FEll As rAin, Filling thE DEEpEst BAsins to proDuCE thE First oCEAns.
thE Fourth stAgE, slow surFACE Evolution, hAs ContinuED For thE lAst 3.5 Billion yEArs or morE.
【多选题】 Our order of high-speed computers is scheduled to arrive __________ today or tomorrow.
A．or
B．on
C．both
D．either
A．or
B．on
C．both
D．either
【单选题】 In the late 1930's and early 1940's, Jacob Lawrence created many paintings _________ the lives of famous African American activists.
A．Portrayed
B．portrayed them
C．that they portrayed
D．that portrayed
A．Portrayed
B．portrayed them
C．that they portrayed
D．that portrayed
【单选题】 The word "distinct" in line 17 is closest in meaning to
A．( visible
B．( gaseous
C．( separate
D．( new
A．( visible
B．( gaseous
C．( separate
D．( new
【单选题】 Which of the following is mentioned as supporting the Pleistocene overkill hypothesis
A．( Many of the animals that became extinct were quite larg
B．( Humans migrated into certain regions around the time that major extinctions occurre
C．( There is evidence that new species were arriving in areas inhabited by human
D．( Humans began to keep and care for certain animal
A．( Many of the animals that became extinct were quite larg
B．( Humans migrated into certain regions around the time that major extinctions occurre
C．( There is evidence that new species were arriving in areas inhabited by human
D．( Humans began to keep and care for certain animal
【单选题】wAtErAnD、liFE、on mArs
1thE prEsEnCE or ABsEnCE oF wAtEr hAs A DirECt BEAring on thE possiBility oF liFE on othEr plAnEts. in thE ninEtEEnth CEntury, it wAs Commonly ACCEptED thAt liFE, pErhAps EvEn intElligEnt liFE, wAs wiDEsprEAD in thE solAr systEm, AnD mArs wAs An oBvious tArgEt in thE sEArCh For liFE. nEw photogrAphiC tEChnology oFFErED A wAy For AstronomErs to lEArn morE ABout thE rED plAnEt. in 1888, itAliAn AstronomEr giovAnni sChiApArElli proDuCED imAgEs thAt showED A nEtwork oF long, thin, DArk linEs Crossing thE surFACE oF mArs. hE CAllED thEsE FEAturEs CAnAli in itAliAn, whiCh BECAmE "CAnAls" or "ChAnnEls" inEnglish. thE strAngE AppEArAnCE oF thE CAnAls suggEstED to somE sCiEntists thAt thEy hAD BEEn FormED ArtiFiCiAlly rAthEr thAn nAturAlly. thE mystEry DEEpEnED whEn sChiApArElli oBsErvED thAt mAny oF thE CAnAls in thE photogrAphs wErE ACtuAlly DouBlE.
2othEr photogrAphiC imAgEs oF mArs rEvEAlED its sEAsonAlly ChAnging polAr iCE CAps AnD FEAturEs thAt AppEArED to BE AnCiEnt islAnDs loCAtED in whAt wAs now A Dry strEAmBED、whEn thE islAnDs wErE First DisCovErED, somE sCiEntists spECulAtED thAt A thiCk wAtEr-lADEn AtmosphErE CApABlE oF gEnErAting hEAvy rAins hAD onCE ExistED on mArs. howEvEr, othErs rEmAinED unConvinCED oF thE prEsEnCE oF wAtEr. thEn, in 1963, A tEAm oF AstronomErs oBtAinED A gooD photogrAphiC plAtE oF thE nEAr-inFrArED spECtrum oF mArs. thE photogrAph showED thAt, FAintly But DEFinitEly, wAtEr vApor linEs CoulD BE sEEn. this photogrAph EstABlishED thAt thErE rEAlly wAs wAtEr on mArs, though thE Amount wAs vEry smAll. toDAy, thE prEsEnCE oF wAtEr vApor in thE mArtiAn AtmosphErE is gEnErAlly ACCEptED, As is thE BEliEF thAt thE AtmosphErE wAs onCE muCh DEnsEr thAn it is now, with A muCh grEAtEr ABunDAnCE oF wAtEr vApor.
3thE surFACE oF mArs is Dry toDAy, But it DoEs ContAin signiFiCAnt Amounts oF iCE AnD signs thAt liquiD wAtEr onCE FlowED ovEr thE plAnEt.All oF thE loCAtions whErE EviDEnCE oF wAtEr hAs BEEn FounD ArE AnCiEnt, proBABly FormED vEry EArly in mArtiAn history.DAtA trAnsmittED From spACECrAFt on mArs in 2004 hAvE rEvEAlED thAt wAtEr wAs onCE Common ACross A vAst rEgion oF thE plAnEt, possiBly As shAllow lAkEs or sEAs thAt DriED out AnD thEn FillED up AgAin. thErE ArE signs thAt thE winD BlEw DEBris ArounD During Dry stAgEs. thEsE sEAs AnD lAkEs ExtEnDED ACross hunDrEDs oF thousAnDs oF squArE milEs, CrEAting hABitABlE ConDitions During long strEtChEs oF timE Billions oF yEArs Ago.
4 EviDEnCE oF wAtEr inCluDEs thE prEsEnCE oF vArious minErAls known As EvAporAtEs, DEposits lEFt BEhinD whEn liquiD wAtEr turns to vApor. smAll ArEAs oF minErAl DEposits hAvE BEEn FounD in vAllEs mArinEris, A hugE holE on mArs thAt is lArgEr thAn thE grAnDCAnyon onEArth. thE minErAls thErE ContAin wAtEr, so thEy hAD to BE FormED in thE prEsEnCE oF wAtEr. gEologiC rEsEArCh hAs Also turnED up ClAy AnD gypsum DEposits thAt wErE FormED By wAtEr in thE soil. roCks thAt ClEArly FormED in wAtEr ExtEnD throughout 300 mEtErs oF lAyErED mAtEriAls in sEvErAl loCAtions ACross thE mArtiAn plAins. thE lAyErs wErE Built up ovEr timE, whiCh mEAns wAtEr wAs prEsEnt, At lEAst tEmporArily, For ExtEnDED pErioDs on AnCiEnt mArs.
5 BEsiDEs thE iCE pACks At mArs’s polEs, AstronomErs hAvE DisCovErED A FrozEn sEA nEAr its EquAtor. this FrozEn sEA is thE sizE oF thE north sEA onEArth AnD AppEArs similAr to thE iCE pACks onAntArCtiCA、sCiEntists hAvE Also DEtECtED EviDEnCE oF lAvA Flows 20 million yEArs Ago As wEll As signs thAt somE volCAnoEs mAy still BE ACtivE. sEvErAl rECEntly FormED volCAniC ConEs nEAr mArs’s north polE inDiCAtE thAt thE plAnEt’s CorE mAy intErACt with thE surFACE, mEAning thErE wAs Both wArmth AnD moisturE in thE rECEnt pAs-CirCumstAnCEs thAt might hAvE supportED liFE.
6liquiD wAtEr is thE kEy ingrEDiEnt For liFE As wE know it. oF All thE othEr plAnEts in thE solAr systEm, mArs is most likEEArth. thE FACt th
1thE prEsEnCE or ABsEnCE oF wAtEr hAs A DirECt BEAring on thE possiBility oF liFE on othEr plAnEts. in thE ninEtEEnth CEntury, it wAs Commonly ACCEptED thAt liFE, pErhAps EvEn intElligEnt liFE, wAs wiDEsprEAD in thE solAr systEm, AnD mArs wAs An oBvious tArgEt in thE sEArCh For liFE. nEw photogrAphiC tEChnology oFFErED A wAy For AstronomErs to lEArn morE ABout thE rED plAnEt. in 1888, itAliAn AstronomEr giovAnni sChiApArElli proDuCED imAgEs thAt showED A nEtwork oF long, thin, DArk linEs Crossing thE surFACE oF mArs. hE CAllED thEsE FEAturEs CAnAli in itAliAn, whiCh BECAmE "CAnAls" or "ChAnnEls" inEnglish. thE strAngE AppEArAnCE oF thE CAnAls suggEstED to somE sCiEntists thAt thEy hAD BEEn FormED ArtiFiCiAlly rAthEr thAn nAturAlly. thE mystEry DEEpEnED whEn sChiApArElli oBsErvED thAt mAny oF thE CAnAls in thE photogrAphs wErE ACtuAlly DouBlE.
2othEr photogrAphiC imAgEs oF mArs rEvEAlED its sEAsonAlly ChAnging polAr iCE CAps AnD FEAturEs thAt AppEArED to BE AnCiEnt islAnDs loCAtED in whAt wAs now A Dry strEAmBED、whEn thE islAnDs wErE First DisCovErED, somE sCiEntists spECulAtED thAt A thiCk wAtEr-lADEn AtmosphErE CApABlE oF gEnErAting hEAvy rAins hAD onCE ExistED on mArs. howEvEr, othErs rEmAinED unConvinCED oF thE prEsEnCE oF wAtEr. thEn, in 1963, A tEAm oF AstronomErs oBtAinED A gooD photogrAphiC plAtE oF thE nEAr-inFrArED spECtrum oF mArs. thE photogrAph showED thAt, FAintly But DEFinitEly, wAtEr vApor linEs CoulD BE sEEn. this photogrAph EstABlishED thAt thErE rEAlly wAs wAtEr on mArs, though thE Amount wAs vEry smAll. toDAy, thE prEsEnCE oF wAtEr vApor in thE mArtiAn AtmosphErE is gEnErAlly ACCEptED, As is thE BEliEF thAt thE AtmosphErE wAs onCE muCh DEnsEr thAn it is now, with A muCh grEAtEr ABunDAnCE oF wAtEr vApor.
3thE surFACE oF mArs is Dry toDAy, But it DoEs ContAin signiFiCAnt Amounts oF iCE AnD signs thAt liquiD wAtEr onCE FlowED ovEr thE plAnEt.All oF thE loCAtions whErE EviDEnCE oF wAtEr hAs BEEn FounD ArE AnCiEnt, proBABly FormED vEry EArly in mArtiAn history.DAtA trAnsmittED From spACECrAFt on mArs in 2004 hAvE rEvEAlED thAt wAtEr wAs onCE Common ACross A vAst rEgion oF thE plAnEt, possiBly As shAllow lAkEs or sEAs thAt DriED out AnD thEn FillED up AgAin. thErE ArE signs thAt thE winD BlEw DEBris ArounD During Dry stAgEs. thEsE sEAs AnD lAkEs ExtEnDED ACross hunDrEDs oF thousAnDs oF squArE milEs, CrEAting hABitABlE ConDitions During long strEtChEs oF timE Billions oF yEArs Ago.
4 EviDEnCE oF wAtEr inCluDEs thE prEsEnCE oF vArious minErAls known As EvAporAtEs, DEposits lEFt BEhinD whEn liquiD wAtEr turns to vApor. smAll ArEAs oF minErAl DEposits hAvE BEEn FounD in vAllEs mArinEris, A hugE holE on mArs thAt is lArgEr thAn thE grAnDCAnyon onEArth. thE minErAls thErE ContAin wAtEr, so thEy hAD to BE FormED in thE prEsEnCE oF wAtEr. gEologiC rEsEArCh hAs Also turnED up ClAy AnD gypsum DEposits thAt wErE FormED By wAtEr in thE soil. roCks thAt ClEArly FormED in wAtEr ExtEnD throughout 300 mEtErs oF lAyErED mAtEriAls in sEvErAl loCAtions ACross thE mArtiAn plAins. thE lAyErs wErE Built up ovEr timE, whiCh mEAns wAtEr wAs prEsEnt, At lEAst tEmporArily, For ExtEnDED pErioDs on AnCiEnt mArs.
5 BEsiDEs thE iCE pACks At mArs’s polEs, AstronomErs hAvE DisCovErED A FrozEn sEA nEAr its EquAtor. this FrozEn sEA is thE sizE oF thE north sEA onEArth AnD AppEArs similAr to thE iCE pACks onAntArCtiCA、sCiEntists hAvE Also DEtECtED EviDEnCE oF lAvA Flows 20 million yEArs Ago As wEll As signs thAt somE volCAnoEs mAy still BE ACtivE. sEvErAl rECEntly FormED volCAniC ConEs nEAr mArs’s north polE inDiCAtE thAt thE plAnEt’s CorE mAy intErACt with thE surFACE, mEAning thErE wAs Both wArmth AnD moisturE in thE rECEnt pAs-CirCumstAnCEs thAt might hAvE supportED liFE.
6liquiD wAtEr is thE kEy ingrEDiEnt For liFE As wE know it. oF All thE othEr plAnEts in thE solAr systEm, mArs is most likEEArth. thE FACt th
【单选题】Why does the professor say this
A、To get the exact number of students who can operate a computer.
B、To ask a warm-up question and lead to the topic of his lecture.
C、To check how many students have good skills of operation.
D、To show the popularity of using computers in students’ life.
A、To get the exact number of students who can operate a computer.
B、To ask a warm-up question and lead to the topic of his lecture.
C、To check how many students have good skills of operation.
D、To show the popularity of using computers in students’ life.
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