阅读下面短文,用文中括号内所给动词的适当形式填空快啊急用
阅读下面短文,用文中括号内所给动词的适当形式填空.
Forestshelptokeepwaterfromrunningaway,sodrought（干旱）doesn'toftenhappen．Chinesepeoplehavebuilta"GreatWall"oftrees,millionsoftreesacrossthenorthernpartofthecountry．
TheGreatGreenWall1________（be）7,000kilometreslong,anditwillstopthewindfrom2________（blow）theearthaway．It3________already________（save）alotofland．
WangFengisaworkeratYulininShanxiProvince．He4________（work）ontheGreatGreenWallwithmanyotherpeople．We5________（visit）himathisworkplaceandwhenwesawhimhe6________（work）amongthetrees．Hetoldussomethingabouthiswork"Wemust7________（plant）manythousandsoftreeseveryyear,"hesaid"Youseeallthosesmalltreesoverthereonthathill?Thatwassandfiveyearsago．Nowit'sayoungforest!Inafewyears'time,we8________（cover）thosemountainswithtrees,too!"Hepointedtothehighmountainsfaraway．
Wasitdifficult9________（work）ontheGreatGreenWall?
Yes,It'shardwork．butit'sveryimportant．Theonlyproblemiswehaveto10________（grow）ourownfood．ButthankstotheGreatGreenWall,thelandproducesmorecrops．Sothemoretreesthereare,thebetterharvestwehave．"
![【已知函数f(x)＝exx−a（a＜0）（1）求函数f（x）的定义域及单调区间；（2）若实数x∈（a，0]时，不等式f(x)≥12恒成立，求a的取值范围．】](/UploadFile/wdimg/2071/874241844/26/3155148506.jpg)
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