单项选择题Examine this statement: RMAN >BACKUP FORMAT ’ BACKUP df_%d_%s_%p.bus1 DATABASE filesperset = 2; What state must the target database be in for you to use this RMAN command?()
A.The target database must be open.
B.The target database must be closed.
C.The target database must be mounted.
D.The target database must be mounted or open.