Forhundredsofyears,thecriminallaw(刑法)hasbeenbuiltaroundtheideathatwrongdoersmustbepunishedfortheircrimes.Themostbasicargumentforpunishmentisthatitpreserveslawandorderandrespectsforauthority.Fromthispointofview，punishmentdoestwothings.Itupholdsthelaw，anditpreventsothersfromthinkingtheycangetawaywithdoingthesamethingwithoutpunishment.Punishmentisbasedontheideathatmanypeoplehaveabarelycontrolleddesiretoactinforbiddenways.Oneofthebestwaystoreducecrimeistoreformorrehabilitate(改造)habitualcriminals.Themainproblemisnotthefirstoffenderorthepettythiefbuttherepeatedoffenderwhocommitsincreasinglyseriouscrimes.Accordingtocriminologists，crimewoulddecreasegreatlyifallsuchoffenderscouldbeturnedawayfromwrongdoing.ButU.S.prisonshavehadlittlesuccessinrehabilitatinginmates.Abouttwo-thirdsofthepeoplearrestedinanyyearhaveapreviouscriminalrecord.Rehabilitation(改造)ofcriminalscouldprobablybeimprovedgreatlyifexpertscouldprovidetherightkindofprogramfordifferenttypesofoffenders.Criminalsvarywidelyinthekindsofcrimestheycommit，theiremotionalproblems，andtheirsocialandeconomicbackgrounds.Notalloffenderscanbehelpedbythesametreatment.Manyrequiretheaidofphysicians,psychiatrists,orpsychologists.Othersrespondwelltoeducationalorvocationaltraining.Intheearly1990s,therewereabout1,300,000criminalsinU.S.city,county,state,andfederalcorrectionalinstitutions，andabout500,000morewereoutonparole.Societyspentmorethan$15billiontooperateprisonsandrelatedinstitutionsyearly,butonlyasmallpartofthissumwenttoprovidetreatment.Nearlyallthefundswereusedtofeedandclotheprisonersandtokeepthemundercontrol.Sincethe1ate1970s,however,therehasbeenatrendtowardpunishmentratherthanrehabilitationofoffenders.Prisonsentences(徒刑)arelonger.CapitalpunishmentshavebeenusedmorefrequentlysincetheU.S.SupremeCourtliftedadeathpenaltybanin1976.Nevertheless,crimepreventionshouldaimtopreventpeoplefrombecomingcriminalsinthefirstplace.Suchagoalprobablywouldbenefitfromreformprogramsinurbanslums.Theseprogramswouldincludeimprovedhousing,schools,andrecreationprogramsandincreasedjobopportunities.Therearemanyotherwaystoreducecrime.Peoplecanbeeducatedorpersuadedtotakegreaterprecautionsagainstcrime.Theycanbetaught,forexample,howtoprotecttheirhomesfromburglary.Automobiletheftswoulddropsharplyifdriversremovedtheirkeysandlockedtheircarswhenleavingthem.Betterlightinghelpsdiscouragepurse-snatchingsandotherrobberiesoncitystreetsandinparks.Manyexpertsbelievethatstrictgun-licensinglawswouldgreatlyreducecrime.15.Theauthorconcludesthepassagebypointingoutthat____.