5、.toknock;smashingB.knocking;smashedC.knocked;smashing D.knocking;smashing11.BeforeCtheofficeshealwaysmakessurethelights.A.left;turnoffB.leaving;toturnoffC.leave;turningoffD.toleave;inturningoff12.Bcomputershavegreatlychangedourwayoflifeisauniversallyacceptedfact.A.Modern B.ThatmodernC.Whatmodern D.