2025年CFA一级道德与专业标准专项测试（含答案）

2025年CFA一级道德与专业标准专项测试（含答案）考试时间：______分钟总分：______分姓名：______指示：请根据你对CFA一级道德与专业标准知识的理解，从以下选项中选择最恰当的一项。1.Ananalystismaintainingarelationshipwithaformerportfoliomanagerwhonowworksforacompetitor.Thecompetitorhasrecentlylaunchedanewinvestmentproductthattheportfoliomanagerisheavilymarketing.Theanalystoccasionallyreceivesnon-publicinformationfromthisformermanageraboutthecompetitor'snewproduct.AccordingtoStandardI(A)-LoyaltytotheClient,whichofthefollowingactions,ifany,istheanalystpermittedtotake?a.Usethenon-publicinformationtomakeinvestmentrecommendationstoexistingclientsregardingthecompetitor'sproduct.b.Sharethenon-publicinformationwithotheranalystsinthefirmforresearchpurposes.c.Informtheportfoliomanagerthattheanalystcannotusetheinformationduetopotentialconflictsofinterest.d.Refrainfromusingtheinformationandreportthereceivingofnon-publicinformationtothefirm'scompliancedepartment.2.Aninvestmentmanagerhasreceivedalargegrantfromauniversitytoconductresearch.Theresearchwillbepublishedandthemanagerwillbelistedasaco-author.AccordingtoStandardVI(A)-IndependenceandObjectivity,whichofthefollowingisthemanagerrequiredtoconsiderwhenconductingtheresearch?a.Ensuringtheresearchfindingshaveapositiveimpactonthemanager'scareerprospects.b.Disclosinganypotentialconflictsofinterestarisingfromthegrant,includingthepotentialperceptionofbias.c.Prioritizingtheuniversity'sadministrativeneedsovertheresearchobjectives.d.Usingthegrantmoneytofundpersonaltravelduringtheresearchperiod.3.Aportfoliomanagerispreparingamarketingbrochureforanewinvestmentstrategy.Thebrochureincludesstatementssuchas"Consistentlyoutperformsthemarket"and"Lowestriskamongsimilarstrategies."AccordingtoStandardVII(A)-MisleadingCommunications,whichofthefollowingstatements,iftrue,wouldmakethebrochuremisleading?a.Thestrategyhasoutperformedthemarketbenchmarkoverthepastthreeyearsinbacktesting.b.Themanageruses"similarstrategies"inthebrochuretorefertoadefinedpeergroupof10strategies.c.Thestatementsarequalifiedwithappropriatecaveatsregardingpastperformanceisnotindicativeoffutureresults.d.Thebrochurealsoincludesdetailedriskmetricsandadescriptionofthestrategy'smethodology.4.Anassociateinaninvestmentbankingdepartmentisattendingaconferencewhereapotentialclientispresent.Theassociatelearnsthattheclientisconsideringacquiringoneofthefirm'stargetcompanies.Theassociatesharesthisnon-publicinformationwithaclosefriendwhoownsstockinthetargetcompany.Thefriendmakessubstantialprofitsfromthisinformation.AccordingtoStandardI(B)-AvoidingConflictsofInterestandStandardII(A)-LoyaltytotheEmployer,whichofthefollowingbestdescribesthepotentialviolation?a.TheassociateviolatedStandardI(B)onlybecausetheinformationwassharedinappropriately.b.TheassociateviolatedStandardII(A)onlybecausethefriendprofitedfromthefirm'sinformation.c.TheassociateviolatedbothStandardsI(B)andII(A)duetotheunauthorizeddisclosureofnon-public,materialinformationandthecreationofapersonalbenefitderivedfromfirmresources.d.Noviolationoccurredastheassociatedidnotdirectlyprofitfromtheinformationandthefriend'sactionswereindependent.5.ALevelICFAcandidateispreparingfortheexamandusesacommercialstudypackagerecommendedbythecandidate'semployer.Thestudypackageincludespracticequestionsthatareverysimilartoquestionspreviouslyusedinthefirm'sinternalexams.Thecandidatesharesthesepracticequestionswithanothercandidatewhoisnotemployedbythefirm.AccordingtoStandardVIII(A)-ProfessionalConductRegardingContinuingEducation,whichofthefollowingdescribestheethicalissue?a.Theuseofthecommercialstudypackagewithouttheemployer'sapprovalviolatesStandardVIII(A).b.Sharingthepracticequestionsviolatesthecandidate'sagreementwiththecommercialprovider,butdoesnotviolateCFAInstituteStandards.c.Sharingquestionsthatwerederivedfromthefirm'scopyrightedmaterialcouldpotentiallyviolateStandardXI(A)-Misconductifitleadstoanunfairadvantage.d.Thecandidate'sactionsdonotviolateanyCFAInstituteStandardsaslongasthestudypackageiscommerciallyavailable.6.Anequityresearchanalystcoversthetechnologysector.Asignificantportionofthefirm'srevenuecomesfromalargetechnologyclientthatprovidesdataandaccess.Theanalyst'sperformancereviewisheavilyweightedtowardsmeetingtheclient'sneedsandgeneratingpositivereports.AccordingtoStandardI(C)-ObjectivityandStandardII(B)-ConflictsofInterest:PrioritizingClientInterest,whichofthefollowingactions,iftakenbytheanalyst,mostclearlydemonstratesaconflictthatneedstobemanaged?a.Theanalystrequestsadditionaldatafromtheclienttoimprovethequalityoftheirreports.b.Theanalystdisclosesintheirreportsthatwhilethecompanyhasstrongfundamentals,theclientrelationshipinfluencesthefrequencyofreportdistribution.c.Theanalystmaintainsaseparateresearchprocessandconclusionsbutagreestodelaypublicationiftheclientrequestsabriefwaitingperiodtoavoidmarketdisruption.d.Theanalyst'sbonusissolelybasedonmeetingpredefinedresearchqualitymetricsagreeduponbythefirm,independentofclientsatisfaction.7.Aninvestmentadvisorrecommendsonlysecuritiesthataredistributedbythefirmwheretheadvisorworks.Thefirmpaystheadvisoracommissionbasedonthevolumeofsales.Whichofthefollowingbestdescribesthestandardthatprimarilygovernsthispractice?a.StandardI(A)-LoyaltytotheClientb.StandardII(B)-ConflictsofInterest:PrioritizingClientInterestc.StandardIII(A)-LoyaltytotheEmployerd.StandardV(A)-CommunicationofResearchFindings8.Duringateammeeting,aportfoliomanagermentionsthatacompetitor'snewproductlaunchlookspromisingbasedonpreliminaryinformation.Anotheranalystinthemeetingsharesthisinformationwithaclosefriendwhoworksatthecompetitorcompany.Thefriendusesthisinformationtoadvisetheirfirm'sclientstobuysharesinthecompetitor.Theportfoliomanagerlaterlearnsthatthefriend'sfirm'sportfoliosignificantlyoutperformedtheirsduringtheproductlaunchperiod.AccordingtoStandardI(B)-AvoidingConflictsofInterestandStandardII(C)-ConflictsofInterest:PersonalFinances,whichofthefollowingrepresentsapotentialconflictofinterestfortheportfoliomanager?a.TheportfoliomanagermayhaveviolatedStandardI(B)iftheysharednon-publicinformation,butthereisnoviolationofStandardII(C).b.Theportfoliomanager'sactionsdonotcreateaconflictofinterestastheydidnotdirectlybenefitfinancially.c.TheportfoliomanagercreatedanindirectconflictofinterestunderStandardII(C)becausetheirteam'sanalysis(whichmayhaveinfluencedthecompetitor'sfriend)contributedtothefriend'sfirm'sprofitablerecommendation.d.Thepotentialviolationlieswiththeanalystwhosharedtheinformationwiththefriend,nottheportfoliomanager.9.Aninvestmentbankerispreparingtorecommendacompanyforaninitialpublicoffering(IPO).Thebankerhasbeendevelopingastrongrelationshipwiththecompany'smanagementteamoverthepastyear.Thebanker'scompensationfortheIPOassignmentisbasedonthetotalproceedsoftheoffering.AccordingtoStandardI(C)-ObjectivityandFairDealing,whichofthefollowingactionsbythebankercouldpotentiallycompromisetheirobjectivity?a.Thebankerensuresthattheprospectusaccuratelydisclosesallmaterialrisksassociatedwiththeinvestment.b.ThebankerrequeststhatthecompanyprovidedetailedfinancialprojectionstosupporttheIPOvaluation.c.Thebankeragreestoprioritizethecompany'sIPOtimelinebasedonthemanagementteam'spreference,evenifitconflictswithmarketconditions.d.Thebankerdisclosesinmarketingmaterialsthatthefirmhasalong-standingtrackrecordofsuccessfulIPOexecutions.10.Aportfoliomanagerisconsideringincludingasmall,emergingmarketcompanyintheportfolio.Thecompanyisnotwidelyfollowed,anditsfinancialsarenotregularlyauditedbyarecognizedfirm.Theportfoliomanagerreliesonasingle,informalreportfromacolleaguewhovisitedthecompanyseveralmonthsago.AccordingtoStandardVI(B)-DueDiligenceandVI(C)-DisclosingConflicts,whichofthefollowingactions,iftaken,wouldbemostconsistentwiththestandards?a.Theportfoliomanagerincludesthestockintheportfoliobasedonthecolleague'sreportwithoutfurtherverification,asthecompanyisconsideredagoodopportunity.b.Theportfoliomanagerconductsminimaladditionalresearchbutincludesthestock,disclosingthattheinformationbaseislimited.c.Theportfoliomanagerrequestsadditionalreportsfromothersources,includingаудиторскаяпроверка(auditorreview)ifpossible,beforemakingadecision.d.Theportfoliomanagerincludesthestockbutdoesnotdisclosetherelianceonasingle,informalreportduetoconcernsaboutrevealingperceivedshort-comings.11.Twoanalystsatthesamefirmarecoveringdifferentcompanieswithinthesameindustry.Oneanalystdiscoversthattheircompany'sproductissignificantlysuperiortothecompetitor'sproductcoveredbytheotheranalyst.Thefirstanalystishesitanttosharethisinformationdirectlywiththesecondanalystforfearofrevealingproprietaryinsights.However,thefirmhasapolicyencouraginginformationsharingamonganalystsforthebenefitoftheentirefirm.AccordingtoStandardI(C)-ObjectivityandStandardIV(C)-CommunicationofResearchFindings,whichofthefollowingactionswouldbemostappropriate?a.Thefirstanalystsharesthecompetitiveinformationinageneral,non-specificwayduringateammeetingtoencouragebroaderindustrydiscussion.b.Thefirstanalystavoidssharinganyinformationandfocusessolelyontheirowncompany'sresearchoutput.c.Thefirstanalystdirectlyemailsthespecificcompetitivedatatothesecondanalyst,explainingitisproprietarybutencouragingthemtoconducttheirownindependentverification.d.Thefirstanalystpresentsthefindingsinafirm-wideconferencecall,attributingtheanalysistotheirteamwhilehighlightingthecompetitiveadvantageswithoutrevealingspecificdata.12.Anassociateintheresearchdepartmentiswritingareportonacompany.Thecompany'sboardofdirectorsrecentlyapprovedasignificantstockbuybackprogram.Theassociateincludesastrong"Buy"recommendationinthereport,heavilyemphasizingthepotentialpositiveimpactofthebuybackonearningspershare(EPS).However,theassociateknowsthattheboard'sdecisionwasheavilyinfluencedbyaninvestmentbankthatperformedthevaluationanalysisforthebuyback.AccordingtoStandardI(C)-ObjectivityandStandardV(B)-CommunicationofResearchFindings,whichofthefollowingactionswouldbemostappropriatetomaintainobjectivity?a.Theassociateincludesacautionarynoteinthereportacknowledgingtheboard'sdecisionbutfocusesprimarilyonthecompany'sstandalonefundamentals.b.Theassociateincludesdetailedfootnotesabouttheinvestmentbank'sroleinthebuybackdecisionanditspotentialinfluenceonEPS.c.Theassociatedowngradestherecommendationto"Hold"tomitigatetheperceivedinfluencefromtheinvestmentbank'sanalysis.d.Theassociatedoesnotmentiontheinvestmentbank'sinvolvementandproceedswiththe"Buy"recommendationastheanalysissupportsit.13.Aportfoliomanagerisconsideringaddinganewinvestmenttotheportfolio.Theinvestmentinvolvescomplexderivativesthatarenotwidelyunderstoodevenbyotherprofessionalsinthefirm.Themanagerreliesheavilyontheselleroftheinvestmentproductforinformationaboutitsrisksandpotentialreturns.AccordingtoStandardVI(B)-DueDiligenceandVI(C)-DisclosingConflicts,whichofthefollowingactions,iftaken,representsapotentialviolation?a.Themanagerrequestsdetaileddocumentationandstress-testsfromtheproductsellerandhasthefirm'sinternalriskdepartmentreviewthematerial.b.Themanagerincludesaprominentdisclosureinclientreportsaboutthecomplexityoftheinvestmentandtherelianceonthesellerforinformation.c.Themanagerreliesprimarilyontheseller'sinformationwithoutperformingindependentanalysisorseekingalternativeexpertopinions.d.Themanagerdiscussestheinvestmentwithafewtrustedcolleaguesbutultimatelydecidesnottoinvestduetoconcernsaboutunderstandingtheproduct.14.Aninvestmentadvisorispreparingaclientreportthatincludesarecommendationtobuyaparticularstock.Thereportalsoincludesasectiondiscussingthecompany'senvironmental,social,andgovernance(ESG)practices.Theadvisorincludesnegativeinformationaboutthecompany'sESGperformancebutdoesnotprovidesufficientcontextorcomparisontoothercompaniesintheindustry.AccordingtoStandardIII(B)-FairDealingandStandardV(A)-CommunicationofResearchFindings,whichofthefollowingbestdescribesthepotentialissue?a.TheadvisorviolatedStandardV(A)onlybecausetheESGinformationwasnotincludedinthemainrecommendationsection.b.TheadvisorviolatedStandardIII(B)becausethenegativeESGinformationwaspresentedwithoutnecessarycontext,potentiallymisleadingclients.c.NoviolationoccurredastheadvisoraccuratelyreportedtheESGinformationasprovidedbyathird-partyESGratingagency.d.TheadvisorviolatedStandardIII(B)onlyiftheyintentionallymisrepresentedtheESGinformation.15.ALevelICFAcandidateisusingacommercialstudyguidefortheexampreparation.Theguideincludesachapteronethicsthatcontainshypotheticalscenariosandmodelanswers.ThecandidatefindsthatthemodelanswersoftenrelyoninterpretingtheStandardsinawaythatismorelenientthanhowthecandidateunderstandstheStandards.Thecandidatemodifiesthestudyguide'sanswerstoalignmorecloselywiththeirunderstandingoftheStandards.AccordingtoStandardVIII(A)-ProfessionalConductRegardingContinuingEducationandProfessionalDevelopment,whichofthefollowingdescribestheethicalissue?a.Thecandidate'smodificationoftheguideispermissibleaslongastheydonotsharethemodifiedguidewithothers.b.ThecandidateviolatedStandardVIII(A)becausetheyalteredcopyrightedmaterial.c.Thecandidate'sactionsdonotviolateanyCFAInstituteStandards,providedthestudyguideispubliclyavailable.d.ThecandidatemaybeindirectlyviolatingStandardI(C)-Objectivityiftheyadoptthemorelenientinterpretationsuggestedbytheguidewithoutthoroughindependentverification.16.Anequityresearchanalystcoversthepharmaceuticalindustry.Theanalyst'sfirmhasalong-termrelationshipwithamajorpharmaceuticalcompany,includingseveralresearchcollaborationsanddatasharingagreements.Theanalystpreparesareportonanewdrugdevelopedbythecompany.Thereportincludesapositiverecommendationbutalsohighlightspotentialsideeffectsbasedonearlyclinicaltrialdata.AccordingtoStandardI(C)-ObjectivityandStandardII(A)-LoyaltytotheEmployer,whichofthefollowingactions,iftakenbytheanalyst,wouldbemostappropriate?a.Theanalystomitsthediscussionofpotentialsideeffectstomaintainapositivetoneinthereport,asthedrugshowsstrongpromise.b.Theanalystincludesthepotentialsideeffectsbutdownplaystheirsignificancecomparedtothedrug'sbenefits.c.Theanalystensuresthereportaccuratelyreflectsallavailableinformation,includingthepotentialsideeffects,anddisclosesthefirm'scollaborativerelationshipwiththecompany.d.Theanalystrequestsadditionaldatafromthecompanyregardingthesideeffectsbutdoesnotincludethisinthereportuntilmoredefinitivedataisreleased.17.Aportfoliomanagerisconsideringinvestingasignificantportionofaclient'sportfolioinastartupcompany.Thestartuphasnotrackrecordandisnotpubliclytraded.Theportfoliomanagerisfriendswiththefounderofthestartupandbelievesstronglyinthecompany'svision.Themanagerpresentstheinvestmentopportunitytotheclient,highlightingthepotentialhighreturnsbutalsoacknowledgingthehighrisk.Themanagerrecommendstheinvestmentbasedontheirpersonalbeliefinthefounderandthebusinessidea.AccordingtoStandardI(C)-Objectivity,StandardI(B)-AvoidingConflictsofInterest,andStandardIII(B)-FairDealing,whichofthefollowingbestdescribesthepotentialethicalconcern?a.ThemanagerviolatedStandardI(C)onlybecausetheyarebasingtherecommendationonpersonalbeliefratherthanpurelyobjectiveanalysis.b.ThemanagerviolatedStandardI(B)becausetheirfriendshipwiththefoundercreatesapotentialconflictofinterestthatwasnotadequatelydisclosedormanaged.c.ThemanagerviolatedStandardIII(B)becausetheymaybepresentingtheopportunityinabiasedmanner,potentiallymisleadingtheclient.d.Noethicalconcernexistsaslongasthemanagerfullydisclosesthehighriskandtheirpersonalconnectiontothefounder.18.ALevelIICFAcandidateisemployedbyaninvestmentfirm.Thefirm'spolicyrequirescandidatestopasstheLevelIIexambeforebeingpromotedtothenextseniorlevel.Thecandidate'sperformancereviewsandsalaryincreasesaredirectlytiedtopassingtheLevelIIexam.AccordingtoStandardI(C)-ObjectivityandProfessionalIntegrity,whichofthefollowingactions,iftakenbythecandidate,wouldbemostconsistentwiththestandards?a.ThecandidatesharesconfidentialfirminformationwithafriendwhoispreparingfortheLevelIexam.b.Thecandidateusesunauthorizedcommercialmaterialduringtheirpreparationthatwasnotapprovedbythefirm.c.Thecandidatemanagestheirtimeeffectively,preparesdiligentlyusingonlyapprovedresources,andreportsanypotentialconflictsofinterestrelatedtotheirexampreparation.d.Thecandidatediscussesspecific,non-publicresearchfindingsfromtheirteamwithafamilymemberwhoworksinadifferentindustry.19.Aninvestmentadvisorismarketinganewmutualfundthatinvestsexclusivelyincompanieswithstrongenvironmental,social,andgovernance(ESG)ratings.Theadvisorpreparesmarketingmaterialsthatstatethefund"deliverssuperiorrisk-adjustedreturnsduetoitsfocusonESGleaders."Theadvisorknowsthatthefund'sperformancehasbeenaveragecomparedtoitspeers,andtheprimarydriverofitsreturnshasbeensectorallocationratherthanESGselection.AccordingtoStandardVII(A)-MisleadingCommunicationsandStandardV(A)-CommunicationofResearchFindings,whichofthefollowingbestdescribesthepotentialethicalissue?a.TheadvisorviolatedStandardVII(A)becausetheclaimabout"superiorrisk-adjustedreturns"isunsubstantiated.b.Theadvisordidnotviolateanystandardsaslongasthemarketingmaterialsaredistributedtoexistingandprospectiveclients.c.TheadvisorviolatedStandardV(A)becausetheypresentedthefund'ssectorallocationstrategyasifitweretheresultofESGleadership.d.NoviolationoccurredastheadvisoraccuratelydisclosedthatthefundfocusesonESGcompanies,eveniftheperformanceisaverage.20.Aportfoliomanagerisresponsibleforaclientportfolio.Themanagerdiscoversthatasignificantportionoftheportfolioisheldinacompanywhoseboardofdirectorsincludesseveralindividualswhoarealsodirectorsofthemanager'sfirm.Themanagerisawarethatthefirm'scompensationstructureincludesfeesbasedonportfolioperformance.AccordingtoStandardI(B)-AvoidingConflictsofInterestandStandardII(A)-LoyaltytotheClient,whichofthefollowingactions,iftakenbythemanager,wouldbemostappropriate?a.Themanagersellsallholdingsinthecompanyimmediatelytoavoidanypotentialconflict.b.Themanagerinformsthecompliancedepartmentanddisclosesthesituationtotheclient,explainingthepotentialconflictandseekingguidance.c.Themanagercontinuestoholdtheposition,reasoningthattheboardrelationshipsdonotdirectlyimpactthecompany'sfundamentals.d.Themanagerrequeststhatthefirm'scompensationcommitteereviewthefeestructuretodetermineiftheboardrelationshipswarrantareductioninfees.试卷答案1.d解析思路：根据StandardI(A)-LoyaltytotheClient，会员应避免利用非公开信息获取不公平优势。选项d描述了最恰当的做法：拒绝使用非公开信息，并告知来源，这符合避免利益冲突的原则。选项a和b都涉及使用非公开信息，违反了StandardI(A)。选项c的告知义务虽然正确，但未解决使用非公开信息的问题。2.b解析思路：根据StandardVI(A)-IndependenceandObjectivity，研究应独立且客观。接受研究资助本身不违反标准，但必须披露任何可能影响独立性和客观性的潜在利益冲突。选项b强调了披露潜在偏见的重要性，这是维护独立性和客观性的必要步骤。选项a和c与独立性客观性无关。选项d未提及披露义务。3.d解析思路：根据StandardVII(A)-MisleadingCommunications，营销材料中的陈述必须真实、准确，不能误导客户。选项d指出，即使有其他限定语，但陈述本身（“始终优于市场”、“最低风险”）如果缺乏足够证据或上下文，可能构成误导，特别是如果它们暗示了超出实际水平的保证。选项a,b,c均暗示了某种程度的真实性或合格性（如提及回测、定义参照组、风险披露），使得误导性降低。4.c解析思路：根据StandardI(B)-AvoidingConflictsofInterest，会员不应利用职务之便获取非公开、重大的信息并从中获益。根据StandardII(A)-LoyaltytotheEmployer，会员应忠诚于雇主，不得从事损害雇主利益的活动。选项c描述了最清晰的违反：分析师分享了非公开的重大信息给朋友，朋友从中获利，这既违反了避免利益冲突原则（利用职务信息获益），也违反了对雇主的忠诚义务（可能泄露信息并造成损失）。5.c解析思路：根据StandardVIII(A)-ProfessionalConductRegardingContinuingEducation，虽然使用商业指南通常不被禁止，但行为需符合职业行为守则。分享受版权保护的、未经授权的特定练习题（尤其是能提供不公平优势的）可能构成违反StandardXI(A)-Misconduct（不当行为），因为它涉及未经授权使用和传播受版权保护的材料，可能损害考试公平性或违反与提供商的协议。选项a和b不完全准确。选项d过于宽泛。6.b解析思路：根据StandardI(C)-Objectivity和StandardII(B)-ConflictsofInterest:PrioritizingClientInterest，会员应客观公正，并将客户利益置于个人或雇主利益之上。选项b描述了一个真实的冲突：如果业绩评估和奖金与满足大客户的需求紧密挂钩，可能会迫使分析师偏离客观分析，优先考虑客户满意度而非纯粹的客户最佳利益，从而损害客观性。选项a和d描述了符合标准的行为。选项c描述了在合规框架内的做法。7.b解析思路：该情景描述的是销售佣金驱动的推荐行为，这直接关联到StandardII(B)-ConflictsofInterest:PrioritizingClientInterest，即会员不应允许个人财务利益影响其推荐。虽然StandardI(A)和III(A)也适用，但核心问题在于基于销售量而非客户最佳利益的佣金结构，这与优先考虑客户利益的原则直接相关。8.c解析思路：根据StandardI(B)-AvoidingConflictsofInterest，会员不应利用非公开信息获利。根据StandardII(C)-ConflictsofInterest:PersonalFinances，会员应避免因个人财务状况或关系产生利益冲突。情景中，分析师的朋友利用从（可能由该分析师团队贡献信息的）朋友那里获得的优势获利，这构成了一个间接的利益冲突。虽然不是分析师直接获利，但其团队的分析工作间接导致了朋友公司的获利，分析师未能阻止这种情况，可能违反了StandardII(C)关于管理关联方利益冲突的要求。9.c解析思路：根据StandardI(C)-Objectivity，会员在提供专业服务时应保持客观公正。选项c描述了