【Thenoticeonthewallismeantto______theunwantedvisitors，especiallyduringworkinghours．（）A.keepupB.keepoffC.keepfromD.keepback】

　　The notice on the wall is meant to______the unwanted visitors，especially duringworking hours．（）

　　A.keep up

　　B.keep off

　　C.keep from

　　D.keep back