【"WhenitcomestoEarth，there'snotimetowaste，"saystheEarthDayNetwork．Andthatisright．Protectingourenvironmentisveryimportant，andWorldEarthDaywas（16）___in1970toraisepeople'senvironmentalawareness．On】

　　"WhenitcomestoEarth，there'snotimetowaste，"saystheEarthDayNetwork．Andthatisright．Protectingourenvironmentisveryimportant，andWorldEarthDaywas （16）___in1970toraisepeople'senvironmentalawareness．OnApril22，PeoplearoundtheworldcelebrateEarthday．

　　Everyyearthereisaspecial （17）___，andthisyearitis"TreesforEarth"，soEarthDaywillbeallaboutplantingtrees．Theirgoalistoplant7.8billiontrees （18）___thenextfiveyears．

　　That'sabiggoal，andyoumightwonder（19）___treesaresoimportant．Wellforone，theycanhelpstopclimatechange．Carbondioxide （二氧化碳） isachemicalinouratmosphere，but___（20）___maketoomuchofit．Eachpersonmakesabout2.3tonsayear，whichisbadfortheenvironment．

　　Wellguesswhat!Trees （21）___carbondioxideandprotecttheairquality．Plantingnewtreesisimportantbecausepeoplecutdown （22）___trees．Lastyear，therewere3trillion（万亿） treesinthe （23）___，about139billioninChina．ButaccordingtoTime，theworld'stotalnumberhasbeen （24）___cutinhalfsincehumancivilization （文明） began．That'sbecause15billiontreesarecutdowneveryyear．

　　Soweneedtoplantmoretoreplenish （补充） theonese'velost．Onetreecantakein48pounds （21.8kg） ofcarbondioxideperyear．Andit'sstilloneofthecheapestand （25）___waystogetridofcarbondioxide．

　　Butdon'tforgetthatyoucanalsohelptheenvironmentbycuttingdownonhowmuchenergyorwateryouuseeveryday．Everylittlethinghelps!

　　16．A．setB．producedC．createdD．found17．A．nameB．themeC．sayingD．sign18．A．forB．afterC．byD．in19．A．whatB．whyC．whetherD．how20．A．humansB．animalsC．ghostsD．plants21．A．takeoutB．putoutC．takeinD．putin22．A．countlessB．hopelessC．uselessD．endless23．A．wildB．worldC．forestD．space