Self-drivingcars-destinationknown?MrZhangcasuallyglancesattheemptydriver'sseatandsays,"DestinationGrandHotel.Familymode.Start.HThecarrespondsimmediately,easingsmoothlyintothebusytrafficandavoidingobstaclesontheroad.Insidethecar,thefamilyhavechosentheirentertainmentfromapop-updisplaypanel,readyforthejourneyahead.Thisimaginedsceneprovidesalikelyfuturerealityforself-drivingcars,alsoknownas1.(autonomy)vehicles(AVs).However,beforethisevolutionintransportbecomesarevolution,itmustbefullyunderstoodhowself-drivingcarswork.Putsimply,self-drivingcarsmust"see"and"behave"2.(appropriate)tobesafeontheroad.Theydothisthroughvarioushardwareanddeep-learningALCamerasaswellassensorslikeradarandlidarcapturea3.9various)ofdatafromtheexternalenvironment.OncethedataissenttotheAIsystem,the"brain"ofthecar,it4.(analyse)andputtogetherlikeapuzzlesothattheself-drivingcarcan"see"itssurroundingsanddetermineitsposition.Meanwhile,theAlsystemidentifiespatternsfromthedataandlearnsfromthem.Anactionplanisthencreatedtoinstructthecarhowto"behave"inrealtime:stayinthelane,moveintoanotherone,speeduporslowdown.Next,thenecessarymechanicalcontrols,suchastheacceleratorandbrakes,areactivatedbytheAIsystem,allowingthecartomoveinline5.theactionplan.Thismaysoundperfectintheory,butinrealitytechnologicalbarriersinAVdevelopmentexist.Theself-drivingcar'sperceptionsystempresentsone.Roadtrafficintherealworldis6plicatedthatunfamiliarorunexpectedconditionsmayoccuratanytime.Sinceitis7.(reason)forthedatabasetoincludeeverypossibleobjectineverypossibleconditionaheadoftime,thesystemmightnotrecognizeeverythingontheroad.Inonetragicreal-lifecase,aself-drivingcar*sperceptionsystemfailed8.(identity)awhitetruckagainstthebright,sunlitsky.Itassumedthattherewasnoobstacleinitspathanddidnotactivatethebrakes,9.(cause)thedeathofthedriverintheself-drivingcar.Accidentslikethisposethequestionofhowself-drivingcarscanbetterlearnandimprovetheirbehavioursontheroadtoensuresafejourneys.Anotheraspectthatneedscarefulconsiderationistheethicalresponses10.self-drivingcarswouldmakeinspecificcircumstances.TheTrolleyProblemisoftenusedtodiscussdifficultethicalchoicestheymayface.Forexample,shouldthoseintheself-drivingcaralwaysbeprotectedfirstevenifitmeans11.(endanger)thelivesofpedestrians?Shouldaself-drivingcarhitasinglepedestriantoavoidcrashingintoagroupofpedestrians?Andwoulditmakeadifferentdecisionifthepedestrianwereachildoraseniorcitizen?Themoraldilemmathatcomeswithhowtoethicallyprogramself-drivingcarshasyettoberesolved.Besidessuchethicalconcerns,thelegalsituationstheAVindustryislikelytobeconfronted12.havefuelledheateddebates.Inthis13.(emerge)industry,manufacturingandprogrammingstandardsarenotyetuniform.14.,thequalityandsafetyofAVtechnologyisstill15.(challenge)Thiscouldleadtoextraordinarycaseslikewhoshouldbeheldresponsiblewhenself-drivingcarsareinvolvedinaccidents-shoulditbethedriver,thesoftwareprogrammerorthemanufacturer?Manufacturingandprogrammingstandardsfirsthavetobeagreedupontomakeitpossibleforlawcourtstodecidewhois16.faultwhenthingsgowrong.AsadvancesinAVdesignandtechnologyareinprogress,thefinalagreementonlawsandregulationsinthisindustryremains17.(see).Therecanbelittledoubtthat,18.allthechallenges,self-drivingcarswillformpartofourfuture.Thequestionis,whatisnext?Somearguethatself-drivingcarsshouldbeallowedtooperatewithouthumancontrol,19.othersaremorecautiousandbelievethathumanoperation,evenif20.(limit),isnecessaryinsuccessfulAVdesign.Onlytimewillrevealitstruepath.Whilethejourneyaheadisnotwithoutobstacles,theeventualdestinationisboundtobeanothermilestoneforhumankind'samazingvisionand21.(inventive).Keys:l.autonomous2.appropriately3.variety4.isanalysed5.with6.so7.unreasonable8.toidentify9.causing10.That/which/()ll.endangering12.with13.emerging14.Moreover/Furthermore/Besides/Additionally15.beingchallenged.16.at17.tobeseen18.despite19.while20.limited21.inventivenessU3ExtendedReadingRacingtowardsthefuture:alookatChina'shighspeedrailnetworkInthedistance,awhitebullet-nosedtrainisthunderingdownthetrack.Itgrowslargerbytheseconduntiliteventuallyslowsandglidespastthelinesofwaitingpassengers.Asiteasestoastop,itsdoorsopenwithahissandthepassengersboardwitheageranticipation.Thenthedoorscloseandthetraindepartsexactlyontime,fortablyinthewell-equipped,spaciouscarriages,thepassengersknowthattheirjourneyaheadwillbeboth2.(effort)andrelaxing.SuchscenesofcontentedpassengersbeingswiftlytransportedtotheirdestinationsarerepeatedmanytimesadayalloverChina,asfarasthehigh-speedrail(HSR)networkextends.Since2008,theHSRnetwork3.(transport)over10billionpassengers,settingaworldrecord.Therearenowmorethan3,000high-speedtrainsrunningdaily,some4.(reach)speedsofupto350kilometresperhour,thefastestintheworldoftraintransport.Alreadycovering92percentofcitieswithpopulationsthatexceedhalfamillionasof2020,theHSRnetworkreacheseverycornerofthecountry.Withanoverall5.(long)ofaround40,000kilometresinoperation,itnotonlygreatlyenhancesthenationalrailroad's6.(efficient),butalsoservesastheenginethatkeepsthecountry's7.(economy)lifebloodflowing.However,China'shigh-speedrailnetworkwasnotbuiltovernight.TheHSRprojectbeganinthe1990sandithasgrownenormouslysincethen.AkeymilestonewasthereleaseoftheHSRnetworkblueprintin2004,8.theplanfor"fourverticalandfourhorizontal"corridorswasput9..Twelveyearslater,it10.(upgrade)to"eightverticalandeighthorizontal"corridors.Today,Chinaboaststheworld'slongestandmost11.(extend)usedHSRnetwork,andisrightlyconsideredtheworldleaderinHSRconstruction.Thisenormoussuccessis12.(separate)fromthevisionaryleadershipoftheCommunistPartyofChinaaswellasthegreatwisdomoftheChinesepeople.Withinnovationandperseverance,theyhaveclimbedoverhurdlesandpassedonemilestoneafteranother.TheBeijing-Shanghailine,theworld'slongestline13.(build)inonestage,hasthefastesthigh-speedtrains,reducingthetraveltimebetweenBeijingandShanghaifrom14hourstolessthan5hours.TheHarbin-Dalianline,thefirsthigh-coldhigh-speedrailwayintheworld,canoperateat350kilometresperhourintemperaturesaslowas-40℃.TheBeijing-Zhangjiakouline,theworld'sfirstsmarthigh-speedrailway,hassetthestandardforHSRautomaticdriving.TheFuxingElectricMultipleUnit(EMU),whichmadeitsdebutin2017,isanotherremarkableaccomplishmentthatdemonstratestechnicalskillinHSRdesignandconstruction.DevelopedandmanufacturedtotallybyChina,theEMUtrainboasts14.(modern)features,elegantdesignsandadvancedtechnologiesthataresuperior15.thoseofpreviousmodels.Itisbuiltwithalongerlifespanandanenergy-savingdesigntoreduceairresistance.Alltheseachievementsshowcasethewholehearteddevotionofengineers,thetirelesseffortofrailroadworkers,andthestrongsupportofalltheChinesepeople.Itisnosurprisethen16.China'sHSRnetworkhasgrabbedtheattentionofthewholeworld.Inthespiritofinternationalcooperation,Chinahas17.(generosity)exporteditstechnologyandskillstomanycountries,andhelpedthemconstructhigh-speedrailwaylines.ThisisinlinewiththeBeltandRoadInitiative,whichaimstorevivetheancientSilkRoadandconnectthecountriesalongthe