下面哪些選擇工具形成的選區可以被用來定義畫筆的形狀（）
下列哪種格式支持圖層：
水利工程檔案保管期限分為()。
Directions:
Inthissection,thereare10incompletesentences.Youarerequiredtocompleteeachonebydecidingonthemostappropriatewordorwordsfromthe4choicesmarkedA,B,CandD.ThenyoushouldmarkthecorrespondingletterontheAnswerSheetwithasinglelinethroughthecenter.
21、62%ofthepeoplesurveyedsaidtheyalwaysavoided______theirsmartphonesduringmeals.
A.useB.usingC.touseD.used
22、TheHRdepartmentisacriticalpartofemployeewell-beinginanybusiness,nomatter______smallitis.
A.howB.whatC.whereD.which
23、Accordingtotheregulation,inspections______toensurethatthesystemsareingoodcondition.
A.demandedB.havedemandedC.bedemandedD.aredemanded
24、Beforeyouthinkaboutaskingforapromotion,makesurethateitherapositionopeningexists______anewpositionisneededtobecreated.
A.andB.norC.orD.but
25、ThetrafficwasmakingsomuchnoisethatIcouldn'thearwhathe______.
A.issayingB.wassayingC.hassaidD.willsay
26、Ourcompanycultureis______makesussuccessfulincreatingafriendlyandexcitingenvironment.
A.whereB.howC.whatD.why
27、Mostpeopleweregreatlyshockedbythenews______theITcompanyhadgonebankrupt.
A.whatB.howC.whyD.that
28、IwouldprobablytrytofindabetterjobifI______inyourposition.
A.amB.wereC.havebeenD.be
29、Ifyouare______busytoattendthemeeting,youcansendyourassistanttotakeyourplace.
A.veryB.soC.tooD.more
30、Ihadtowaitforanothertwomonthstobeabletohavethecar______.
A.fixingB.fixC.tofixD.fixed
如果選擇了一個前面的歷史記錄，所有位于其后的歷史記錄都無效或變成了灰色顯示，這說明了什么
