Iftheoperation________carefullyprepared,itwouldnothavebeensuccessful.
C
语法题：虚拟语气。
Aftermonthsofvoyage,Columbusarrivedin______laterprovedtobeanewcontinent.
Theprofessoraskedaquestion,andDavid________agoodanswer.
Hisintelligencewill________himtogetascholarshiptocollege.
It is no use arguing _______ the plan because it has been rejected.
If the operation ________ carefully prepared, it would not have been successful.