1.请阅读Passage1，完成第下列问小题。
Passage1
Thesedays,manylargecitybuildingsareequippedwiththeirownair-conditioningsystems.Thesesystemshelpkeepthebuildingscool,buttheycanalsodamagetheenvironment.Sincetheyusealotofelectricity,forinstance,theycontributeindirectlytoglobalwarming.Inaddition,thewaterthatflowsthroughthesystemsisoftencooledusingchemicalscalledchlorofluorocarbons,orCFCs,thatarebelievedtodamagetheEarth′sozonelayer.Recently,though,asystemhasbeenbuiltinthecityofToronto,Canada,thatcoolsbuildingswithlittledamagetotheenvironment.
Inthetraditionalair-conditioningsystemsfoundinmostlargebuildings,waterispumpedthroughthebuildinginacontinuouscycle.Thewaterisfirstcooledtoatemperatureof4℃inmachinescalledchillers.Itisthensenttoindividualunitsthatcooltheairineachroom.Asthewaterflowsthroughthebuilding,itgraduallybecomeswarmer.Finally,itreachestheroof,whereitislefttocooldownnaturallyinawatertower.Afterthatitisreturnedtothechillers,wherethecyclebeginsagain.
TorontoliesontheshoreofLakeOntario,oneofNorthAmerica′sGreatLakes,andthenewsystemmakesuseofcoldwatertakenfromabout80metersbelowthesurfaceofthelake.Atthisdepth,thewaterinthelakeremainsat4℃allyearround.Thisisexactlythetemperaturetowhichthewaterinair-conditioningsystemsiscooled.However,thewaterfromthelakeisnotpumpeddirectlyintotheair-conditioningsystems.Instead,itisusedtocoolthewaterthatisalreadyinsidetheair-conditioningsystems.Afterthat,thelakewaterisaddedtothecity′sordinarywatersupply.
Enwave,thecompanythatdevelopedthisdeep-lakecoolingsystem,saysthatituses75percentlessenergythantraditionalairconditioning.AndsincenoCFCsareused,nodamagecanbecausedtotheozonelayer.Noteverycityislocatednexttoalargelake,butexpertsbelievethatsystemsliketheonebeingusedinTorontocouldbebuiltelsewherebyusingothernaturalsourcesofcoldwater.
{TS}Whatisoneproblemwithtraditionalair-conditioningsystems?