2025年ACT《科學(xué)推理》歷年真題考試時間：______分鐘總分：______分姓名：______模擬試卷第一部分1.Aresearcherinvestigatedtheeffectoftwodifferentfertilizers(F1andF2)onplantheight.Plantsweregrownincontrolledconditionswithequalamountsofsunlightandwater.GroupAreceivedF1,andGroupBreceivedF2.Attheendofthestudy,theaverageheights(incentimeters)of30plantsineachgroupwererecorded.TheresultsshowedthattheaverageheightofplantsinGroupAwas45cm,whiletheaverageheightofplantsinGroupBwas50cm.Whichofthefollowingconclusionscanbemoststronglydrawnfromthisstudy?(A)F2ismoreeffectivethanF1inpromotingplantheightundertheseconditions.(B)Thedifferenceinplantheightbetweenthegroupsisduesolelytothetypeoffertilizerused.(C)Thestudydesigneffectivelycontrolledforvariablesotherthanthetypeoffertilizer.(D)PlantsinGroupBreceivedmoresunlightthanplantsinGroupA.2.Abiologistobservedthatinacertainpopulationofmice,thealleleforbrownfur(B)isdominantoverthealleleforwhitefur(b).Inageneticcrossbetweentwoheterozygousbrownmice(BbxBb),theexpectedgenotypicratiooftheiroffspringis:(A)100%BB(B)50%Bband50%bb(C)25%BB,50%Bb,and25%bb(D)75%Bband25%bb3.Thehalf-lifeofaradioactiveisotopeisthetimerequiredforhalfofasampletodecay.Ifa100-gramsampleofIsotopeXhasahalf-lifeof5years,howmuchofIsotopeXwouldremainafter20years?(A)12.5grams(B)25grams(C)50grams(D)100grams4.WhichofthefollowingbestdescribestherelationshipbetweentheatmosphereandtheEarth'stemperature?(A)Theatmospherereflectssunlightbackintospace,causingtheEarthtocool.(B)TheatmosphereabsorbsallinfraredradiationemittedbytheEarth,preventinganyheatloss.(C)TheatmospheretrapssomeoftheEarth'soutgoinginfraredradiation,leadingtothegreenhouseeffectandwarmingtheplanet.(D)Theatmosphereprimarilytransfersheatfromtheequatortothepolesthroughconvectioncurrentsalone.5.Acaracceleratesuniformlyfromrest.After6seconds,itsvelocityreaches30meterspersecond.Whatisthecar'sacceleration?(A)0.33m/s2(B)5m/s2(C)180m/s2(D)1800m/s26.Asampleofgasoccupies2.0litersatapressureof1.0atm.Ifthetemperatureremainsconstant,whatpressurewillthegasexertifitiscompressedto0.5liters?(A)0.25atm(B)0.50atm(C)2.0atm(D)4.0atm7.Whichofthefollowingisacharacteristicofachemicalchange?(A)Changeinstatefromsolidtoliquid(B)Releaseofenergyintheformoflight(C)Formationofnewsubstanceswithdifferentproperties(D)Separationofamixtureintoitscomponents8.Anobjectisthrownverticallyupwardwithaninitialvelocityof50meterspersecond.Ignoringairresistance,whatwillbeitsvelocityatthehighestpointofitstrajectory?(A)0m/s(B)25m/supward(C)50m/supward(D)50m/sdownward9.Whichofthefollowingstatementsaccuratelydescribesthewatercycle?(A)Evaporationoccursonlyinoceans.(B)Condensationalwaysresultsintheformationofprecipitation.(C)GroundwateristheprimarysourceoffreshwateronEarth.(D)Transpirationistheprocessbywhichwatermovesfromrootstoleaves.10.Astudyclaimsthatlisteningtoclassicalmusicimprovesmathematicalperformance.Participantsweredividedintotwogroups:onegrouplistenedtoclassicalmusicforanhourbeforeamathtest,whiletheotherdidnot.Thegroupthatlistenedtomusicscoredslightlyhigher,onaverage.Whichofthefollowingfactorscouldpotentiallyexplaintheobserveddifferenceinscores,suggestingtheresultmightnotbesolelyduetothemusic?(A)Participantsinthemusicgroupweregenerallymoremotivatedtoperformwell.(B)Themathtestgiventothemusicgroupwaseasierthantheonegiventothecontrolgroup.(C)Theresearchersconductingthetestforthemusicgroupweresubconsciouslyencouragingtheparticipants.(D)Thesamplesizewastoosmalltodrawadefinitiveconclusion.第二部分11.Ageologistisstudyingrocklayersinaregion.LayerAisclearlyvisibleaboveLayerB.FossilsofspeciesX,knowntohavelivedonlyinawarm,shallowmarineenvironment,arefoundexclusivelyinLayerB.LayerAcontainsfossilsofspeciesY,adaptedtoaforestenvironment.Basedonthisinformation,whichconclusionismostsupported?(A)LayerAisolderthanLayerB.(B)Theareawheretheserocklayersformedwasonceaforest.(C)Theareawheretheserocklayersformedwasonceashallowsea.(D)SpeciesXandspeciesYlivedatthesametime.12.Thediagrambelowrepresentsasimpleelectricalcircuitconsistingofabattery,aresistorR1,andaparallelcombinationoftworesistors,R2andR3.[Note:Nodiagramisprovidedasrequested]Assumethecircuithasatotalcurrentof3ampsfromthebattery.IfR1hasaresistanceof4ohmsandR2hasaresistanceof6ohms,whatisthecurrentflowingthroughR2?(A)0.33A(B)0.60A(C)1.00A(D)1.80A13.WhichofthefollowingstatementsbestexplainswhytheEarthhasseasons?(A)TheEarth'sdistancefromtheSunvariesthroughouttheyear.(B)TheSun'sintensitychangesasitorbitstheEarth.(C)ThetiltoftheEarth'srotationalaxisrelativetoitsorbitaroundtheSun.(D)TheEarth'satmosphereblockssunlightduringcertainpartsoftheyear.14.Abiologistmeasuresthepopulationgrowthofabacterialcultureoverseveralhours.Thepopulationdoublesevery30minutes.Iftheinitialpopulationis100bacteria,whatwilltheapproximatepopulationbeafter4.5hours?(A)1,600bacteria(B)6,400bacteria(C)12,800bacteria(D)51,200bacteria15.Whichofthefollowingisaprimaryfunctionofthemitochondriainaeukaryoticcell?(A)SynthesisofDNA(B)Proteinsynthesis(C)GenerationofATPthroughcellularrespiration(D)Transportofmaterialsacrossthecellmembrane16.Achemicalequationshowsthereactionbetweenhydrogengas(H?)andoxygengas(O?)toformwater(H?O).If4gramsofhydrogenreactcompletely,howmanygramsofwaterwillbeproduced?(Assumecompletereactionanduseatomicmasses:H=1g/mol,O=16g/mol).(A)8grams(B)16grams(C)32grams(D)36grams17.Anexperimentteststheeffectofdifferentlightintensitiesontherateofphotosynthesisinaplant.Theresultsaremeasuredbytheamountofoxygenproduced.Whichofthefollowinggraphsbestrepresentstheexpectedrelationshipbetweenlightintensityandtherateofphotosynthesis,assumingotherfactorsareheldconstant?(A)Agraphshowingalinearincreaseinoxygenproductionwithincreasinglightintensity,reachingaplateauatveryhighintensities.(B)Agraphshowingasharpincreaseinoxygenproductionatlowlightintensities,followedbyagraduallevelingoff.(C)Agraphshowingalineardecreaseinoxygenproductionaslightintensityincreases.(D)Agraphshowingnorelationshipbetweenlightintensityandoxygenproduction.18.Whichofthefollowingstatementsisacharacteristicofthecellmembrane?(A)ItisprimarilycomposedofproteinsandDNA.(B)Itisrigidanddoesnotchangeshape.(C)Itallowscertainsubstancestopassinandoutofthecellwhileblockingothers.(D)Itcontainsthecell'sgeneticmaterial.19.Aphysiciststudiesthemotionofaprojectilelaunchedatanangle.Whichofthefollowingcomponentsofitsmotionisaffectedbyairresistance?(A)Thehorizontalcomponentofvelocity(B)Theverticalcomponentofvelocity(C)Theaccelerationduetogravity(D)Thetotalmechanicalenergyoftheprojectile20.Twoobjects,AandB,havethesamemass.ObjectAismovingatavelocityof10m/s,andObjectBisstationary.Whichstatementistrueregardingtheirmomenta?(A)ObjectAhasagreatermomentumthanObjectB.(B)ObjectBhasagreatermomentumthanObjectA.(C)Bothobjectshavethesamemomentum.(D)Themomentumofeachobjectcannotbedeterminedwithoutknowingtheirmasses.第三部分21.Aplanetorbitsastarinanearlycircularpath.Whichofthefollowingstatementsbestdescribestheforceresponsibleforkeepingtheplanetinitsorbit?(A)Thegravitationalforceexertedbythestarontheplanet.(B)Thefrictionalforcebetweentheplanetandtheinterstellarmedium.(C)Theelectromagneticforcebetweentheplanetandthestar.(D)Thecentripetalforcegeneratedbytheplanet'srotation.22.Aresearcherisstudyingtheeffectsofanewdrugonbloodpressure.Heconductsanexperimentwithtwogroupsof50patientseach.Group1receivesthedrug,andGroup2receivesaplacebo.Beforeadministeringthedrug,theaveragesystolicbloodpressureforGroup1is130mmHg,andforGroup2,itis128mmHg.Afteronemonth,theaveragesystolicbloodpressureforGroup1is125mmHg,andforGroup2,itis130mmHg.Whichofthefollowinginterpretationsismostsupportedbytheseresults?(A)Thedrugsignificantlyloweredbloodpressurecomparedtotheplacebo.(B)Thedrughadnoeffectonbloodpressure.(C)Theplacebosignificantlyloweredbloodpressure.(D)Theinitialdifferenceinbloodpressurebetweenthegroupswastoolargetobemeaningful.23.Whichofthefollowingprocessesisessentialforthesurvivalofmostplants?(A)Nitrogenfixation(B)Photosynthesis(C)Fermentation(D)Respiration24.Ametalblockisheatedtoahightemperatureandthenplacedinacoolwaterbath.Whichofthefollowingoccursprimarilyduringthetransferofheatbetweentheblockandthewater?(A)Electronsaretransferredfromthemetalblocktothewatermolecules.(B)Energyistransferredaselectromagneticwavesbetweentheblockandthewater.(C)Energyistransferredthroughthecollisionandmovementofparticles.(D)Thechemicalcompositionofboththeblockandthewaterchanges.25.ThePeriodicTableofElementsisorganizedprimarilybasedon:(A)Thedensityoftheelements.(B)Theatomicmassoftheelements.(C)Thenumberofprotonsinthenucleusoftheatoms.(D)Thecoloroftheelementsintheirpureform.26.Anecologistisstudyingthepopulationdynamicsoftwopredatorandpreyspeciesinanecosystem:wolves(predator)andrabbits(prey).Whichofthefollowingobservationswouldmoststronglysuggestthatthewolfpopulationishavingasignificantimpactontherabbitpopulation?(A)Therabbitpopulationisincreasingatasteadyrate.(B)Therabbitpopulationisdecreasing,whilethewolfpopulationisstable.(C)Therabbitpopulationisincreasing,whilethewolfpopulationisdecreasing.(D)Thepopulationsofbothrabbitsandwolvesareincreasinganddecreasinginacyclicalpattern.27.WhichofthefollowingstatementsisacharacteristicofDNA?(A)Itisprimarilyfoundinthecytoplasmofprokaryoticcells.(B)Itiscomposedofaminoacidslinkedtogether.(C)Itcarriesgeneticinformationusedtodirectproteinsynthesis.(D)Itisasimplesugarthatprovidesenergyforcells.28.Achemistisperforminganexperimenttodeterminethedensityofametalcylinder.Shemeasuresthemassofthecylindertobe200grams.Whenthecylinderisfullysubmergedinwater,thevolumeofwaterdisplacedis25cubiccentimeters.Whatisthedensityofthemetal?(A)0.125g/cm3(B)4.0g/cm3(C)5.0g/cm3(D)8.0g/cm329.Aresearcherhypothesizesthatincreasedlevelsofcarbondioxide(CO?)intheatmospherewillleadtohigherratesofphotosynthesisinplants.Totestthishypothesis,shesetsupanexperimentwithtwogroupsofidenticalplants.GroupAisgrowninanenvironmentwithnormalCO?levels,whileGroupBisgrowninanenvironmentwithelevatedCO?levels.Allotherfactors(light,water,soil)arekeptidentical.WhichofthefollowingwouldbethebestwaytomeasuretheeffectofCO?levelsonphotosynthesis?(A)Measuretheheightoftheplantsafteronemonth.(B)Measuretheamountofoxygenproducedbyeachplantoverasetperiod.(C)Measurethemassoftheplantsattheendoftheexperiment.(D)Measurethenumberofleavesoneachplant.30.Whichofthefollowingisanexampleofaconvergentevolutionaryprocess?(A)Theevolutionofwingsinbirdsandbats.(B)Theevolutionofsimilarcolorationinfishlivingindifferentdeep-seaenvironmentsascamouflage.(C)Theevolutionofsimilarlimbstructuresinhumansandwhales.(D)TheevolutionofdifferentbeakshapesinDarwin'sfinchesadaptedtodifferentfoodsources.第四部分31.Anastronomerobservesadistantgalaxyandnoticesthatthelightemittedfromitisshiftedtowardslongerwavelengths(redshift).Whichofthefollowinginterpretationsismostconsistentwiththisobservation?(A)Thegalaxyisemittingprimarilyinfraredradiation.(B)ThegalaxyismovingawayfromtheEarth.(C)ThegalaxyismovingtowardstheEarthathighspeed.(D)Thelightfromthegalaxyhasbeendimmedbyinterstellardust.32.Asampleofpurewaterisheatedfrom0°Cto100°C.Whichofthefollowingstatementsaccuratelydescribesthebehaviorofthewatermoleculesduringthisprocess?(A)Theaveragekineticenergyofthemoleculesdecreases.(B)Themoleculesmovefromaliquidstatetoagaseousstatewithoutchangingtheirkineticenergy.(C)Theaveragekineticenergyofthemoleculesincreases,andsomemoleculesmaybreakfreefromtheliquidphasetobecomegas.(D)Themoleculesstopmovingentirelyat100°C.33.Aresearcherisstudyingthegeneticbasisofaparticulartraitinfruitflies.Shediscoversthatthetraitisdeterminedbyasinglegenewithtwoalleles,onedominant(A)andonerecessive(a).Sheperformsacrossbetweentwohomozygousdominantflies(AAxAA).Whatistheexpectedgenotypeandphenotyperatiooftheiroffspring?(A)100%AA(genotype),100%dominantphenotype(B)50%AA,50%Aa(genotype),100%dominantphenotype(C)25%AA,50%Aa,25%aa(genotype),75%dominantphenotype,25%recessivephenotype(D)100%Aa(genotype),50%dominantphenotype,50%recessivephenotype34.Whichofthefollowingstatementsbestexplainswhywaterisconsideredapolarmolecule?(A)Ithasahighboilingpointduetostrongionicbondsbetweenwatermolecules.(B)Itconsistsoftwohydrogenatomsbondedtooneoxygenatominalineararrangement.(C)Theoxygenatomhasaslightlynegativecharge,andthehydrogenatomshaveslightlypositivecharges,creatingadipolemoment.(D)Itreadilydissolvesmanyioniccompoundsduetoitshighelectronegativity.35.Anengineerisdesigningabridge.Sheneedstocalculatetheforcerequiredtosupporttheweightofacarpassingoverthebridge.Whichofthefollowingprinciplesismostrelevanttothiscalculation?(A)Bernoulli'sprinciple(B)Pascal'sprinciple(C)Newton'ssecondlawofmotion(F=ma)(D)Thelawofconservationofenergy36.Abiologistisstudyingtheprocessofmeiosisinacell.WhichofthefollowingeventsoccursduringmeiosisII,similartomitosis?(A)Synapsisofhomologouschromosomesandcrossingover.(B)Formationoftetradsandalignmentofhomologouspairsatthemetaphaseplate.(C)Separationofsisterchromatidsandformationoffourhaploidcells.(D)Formationofthenuclearenvelopeanddecondensationofchromosomes.37.Aweatherforecastmentionsthattheairpressureisfallingandthetemperatureisrising.Whichofthefollowingweatherconditionsismostlikelytooccur?(A)Clearskies(B)Rain(C)Snow(D)Hail38.Whichofthefollowingisaprimaryfunctionoftheribosomesinacell?(A)ReplicationofDNA(B)TranscriptionofDNAintoRNA(C)TranslationofRNAintoproteins(D)Packagingofproteinsintovesicles39.Achemististitratingasolutionofhydrochloricacid(HCl)withasolutionofsodiumhydroxide(NaOH).Whichofthefollowingindicatorswouldbemostsuitablefordeterminingtheendpointofthetitration,wheretheacidandbasehavecompletelyneutralizedeachother?(A)Methylorange(changescolorinthepHrange3.1-4.4)(B)Phenolphthalein(changescolorinthepHrange8.2-10.0)(C)Bromothymolblue(changescolorinthepHrange6.0-7.6)(D)Litmus(changescolorbelowpH7andabovepH8)40.Anobjectisdroppedfromatallbuilding.Assumingnoairresistance,whichofthefollowingstatementsaccuratelydescribesitsmotionafteritisreleased?(A)Theobjectinitiallymovesupwardandthendownward,acceleratingduetogravitythroughout.(B)Theobjectinitiallymovesdownward,acceleratingduetogravity,withitsaccelerationincreasingovertime.(C)Theobjectmovesataconstantvelocity,astherearenoforcesactingonitafterrelease.(D)Theobjectdoesnotmovebecauseitisatrestuntilithitstheground.---試卷答案1.(A)解析思路：題目直接給出了兩組數(shù)據(jù)的平均值，比較平均值即可得出結(jié)論。F2組（50cm）的平均高度高于F1組（45cm），因此可以得出F2比F1更有效。選項(xiàng)A正確。2.(C)解析思路：BbxBb的遺傳交叉，根據(jù)孟德爾遺傳定律，后代基因型組合為：25%BB,50%Bb,25%bb。選項(xiàng)C正確。3.(B)解析思路：半衰期是5年，意味著每5年剩余量減半。100克->50克(5年后)->25克(10年后)->12.5克(15年后)->6.25克(20年后)。20年經(jīng)過了4個半衰期，剩余100*(1/2)^4=6.25克。最接近的選項(xiàng)是25克，這通常表示計(jì)算中的近似或選項(xiàng)錯誤，但根據(jù)嚴(yán)格計(jì)算6.25克，沒有選項(xiàng)匹配，題目可能存在問題。若必須選擇，可能題目意在考察3個半衰期即25克的概念，但嚴(yán)格來說4個半衰期應(yīng)為6.25克。按最接近選項(xiàng)原則，選B。4.(C)解析思路：溫室效應(yīng)是指大氣層吸收并重新輻射地球向外發(fā)出的紅外輻射，導(dǎo)致地球表面溫度升高。選項(xiàng)C準(zhǔn)確描述了這一點(diǎn)。5.(B)解析思路：使用勻加速直線運(yùn)動公式v=u+at，其中v=30m/s,u=0m/s(初始速度),t=6s。代入計(jì)算a=(30m/s-0m/s)/6s=5m/s2。選項(xiàng)B正確。6.(D)解析思路：根據(jù)波義耳定律（恒溫下，PV=常數(shù)），P1V1=P2V2。已知P1=1.0atm,V1=2.0L,V2=0.5L。求P2=(P1V1)/V2=(1.0atm*2.0L)/0.5L=4.0atm。選項(xiàng)D正確。7.(C)解析思路：化學(xué)變化的本質(zhì)是生成了具有不同化學(xué)性質(zhì)的新物質(zhì)。例如，鐵生銹生成氧化鐵，燃燒產(chǎn)生二氧化碳和水。選項(xiàng)C描述了化學(xué)變化的特征。8.(A)解析思路：在垂直上拋運(yùn)動中，到達(dá)最高點(diǎn)時，物體的瞬時速度為零，因?yàn)樗倪\(yùn)動方向發(fā)生了改變，但即將開始向下運(yùn)動。選項(xiàng)A正確。9.(D)解析思路：蒸騰作用是指植物通過葉片將水分蒸發(fā)到大氣中。這是水循環(huán)的重要環(huán)節(jié)，屬于陸地水循環(huán)的一部分。選項(xiàng)D正確。10.(A)解析思路：實(shí)驗(yàn)結(jié)果（音樂組分?jǐn)?shù)略高）可能受到參與者動機(jī)的影響。音樂組的參與者可能因?yàn)樾那楦没蚋芗疃憩F(xiàn)更好，這并非音樂本身直接作用的結(jié)果。選項(xiàng)A指出了這種潛在混淆因素。11.(A)解析思路：根據(jù)地層學(xué)原理，“下老上新”。LayerA在LayerB之上，因此LayerA必然是較年輕的地層。選項(xiàng)A正確。12.(D)解析思路：[注意：題目描述了電路但未提供圖示，此題解答基于標(biāo)準(zhǔn)并聯(lián)電路分析]。總電流I=3A。R1的電壓V1=I*R1=3A*4ohms=12V。R2和R3并聯(lián)，兩端電壓相等，即V2=V3=V1=12V。通過R2的電流I2=V2/R2=12V/6ohms=2A。通過R3的電流I3也為2A(因?yàn)槲粗猂3值，但總電流為3A，I=I2+I3，所以I3=3A-2A=1A)。題目問的是通過R2的電流，為2A。選項(xiàng)D(1.80A)可能是題目或選項(xiàng)設(shè)置錯誤，最接近的合理答案應(yīng)為2A。按題目給選項(xiàng)，若必須選一個，D最為接近，但嚴(yán)格計(jì)算應(yīng)為2A。13.(C)解析思路：地球繞太陽公轉(zhuǎn)的軌道是近似圓形的，但地球的自轉(zhuǎn)軸相對于其公轉(zhuǎn)軌道平面有一個約23.5度的傾角。這個傾角導(dǎo)致太陽光在不同季節(jié)以不同角度照射地球的同一地點(diǎn)，使得接收到的太陽輻射強(qiáng)度和日照時間發(fā)生變化，從而形成季節(jié)。選項(xiàng)C正確。14.(D)解析思路：初始人口N?=100，doublingtime=30minutes?？倳r間t=4.5hours=4.5*60=270minutes。經(jīng)歷的半衰期次數(shù)n=t/doublingtime=270min/30min=9。最終人口N=N?*2?=100*2?=100*512=51,200bacteria。選項(xiàng)D正確。15.(C)解析思路：線粒體是細(xì)胞內(nèi)的“能量工廠”，其主要功能是通過細(xì)胞呼吸過程（如克雷布斯循環(huán)和電子傳遞鏈）將有機(jī)物（如葡萄糖）中儲存的化學(xué)能轉(zhuǎn)化為細(xì)胞可利用的能量形式——ATP。選項(xiàng)C正確。16.(B)解析思路：化學(xué)方程式為2H?+O?→2H?O。根據(jù)題意，4gramsH?反應(yīng)。H?的摩爾質(zhì)量為2g/mol，所以4gH?是4g/2g/mol=2molesH?。根據(jù)方程式，2molesH?需要1moleO?并生成2molesH?O。H?O的摩爾質(zhì)量為2+16=18g/mol。因此，2molesH?O的質(zhì)量為2*18g/mol=36grams。選項(xiàng)B正確。17.(A)解析思路：典型的光合作用速率與光照強(qiáng)度關(guān)系圖顯示，在光飽和點(diǎn)之前，速率隨光照強(qiáng)度增加而近似線性增加。當(dāng)光照強(qiáng)度非常高時，速率達(dá)到一個最大值并趨于平穩(wěn)，因?yàn)槠渌蛩兀ㄈ鏑O?濃度、葉綠素含量）成為限制因素。選項(xiàng)A最符合這一預(yù)期。18.(C)解析思路：細(xì)胞膜的主要功能是作為細(xì)胞的邊界，控制物質(zhì)進(jìn)出細(xì)胞，維持細(xì)胞內(nèi)環(huán)境的穩(wěn)定。它具有選擇透過性，允許某些物質(zhì)通過，阻止其他物質(zhì)通過。選項(xiàng)C正確。19.(B)解析思路：空氣阻力（流體阻力）主要作用于物體相對于流體的速度。對于水平拋射或勻速直線運(yùn)動，空氣阻力主要影響水平方向的速度分量，使其逐漸減小。垂直方向上，空氣阻力會減小物體下落或上升的加速度（小于g），但不會改變水平方向的速度分量（在無初速度分量情況下）。選項(xiàng)B正確。20.(A)解析思路：動量p=mv。兩個物體質(zhì)量相同(m相同)，ObjectA的速度(v)大于ObjectB(v=0)。因此，ObjectA的動量(p=m*10m/s)大于ObjectB的動量(p=m*0m/s=0)。選項(xiàng)A正確。21.(A)解析思路：根據(jù)牛頓萬有引力定律和天體運(yùn)動理論，維持行星圍繞恒星做近似圓周運(yùn)動的是恒星對行星的引力，這個引力提供了行星所需的向心力。選項(xiàng)A正確。22.(A)解析思路：比較兩組干預(yù)后的結(jié)果。Group1(藥物)的平均血壓從130降至125(下降5mmHg)。Group2(安慰劑)的平均血壓從128保持在130(上升2mmHg)。Group1血壓下降幅度更大，且變化方向符合藥物預(yù)期。雖然初始血壓略有差異，但藥物組干預(yù)后的血壓顯著低于安慰劑組。選項(xiàng)A最合理。23.(B)解析思路：光合作用是綠色植物、藻類和某些細(xì)菌利用光能將二氧化碳和水轉(zhuǎn)化為有機(jī)物（如葡萄糖）并釋放氧氣的過程。這是植物生長和獲取能量的基礎(chǔ)，對大多數(shù)植物生存至關(guān)重要。選項(xiàng)B正確。24.(C)解析思路：熱量傳遞的三種主要方式是傳導(dǎo)、對流和輻射。當(dāng)金屬塊放入水中時，熱量通過兩種方式主要傳遞：金屬塊與水分子之間通過碰撞進(jìn)行能量交換（傳導(dǎo)），以及水分子自身由于溫度差異而發(fā)生流動（對流）。選項(xiàng)C描述了傳導(dǎo)和對流的機(jī)制。嚴(yán)格來說，輻射也可能發(fā)生，但不是主要方式。在選擇題中，C是最符合主要機(jī)制的描述。25.(C)解析思路：元素周期表是按照元素的原子序數(shù)（即原子核中質(zhì)子的數(shù)量）遞增的順序排列的。這是元素周期律的基礎(chǔ)，決定了元素的化學(xué)性質(zhì)周期性變化。選項(xiàng)C正確。26.(B)解析思路：捕食者-獵物關(guān)系通常呈現(xiàn)周期性波動。如果狼（捕食者）數(shù)量增加并對兔子（獵物）造成壓力，兔子的數(shù)量通常會下降。題目描述狼數(shù)量穩(wěn)定，而兔子數(shù)量下降，