You received these error messages because the client cannot find the desired database：  
ORA-12198： TNS：could not path to destination 
ORA-12203： TNS：unable to connect to destination 
Which action would be appropriate in helping to resolve the errors？（）

A.A
B.B
C.C
D.D

A.Each target database requires its own recover catalog. 
B.RMAN scripts can be stored in the recovery catalog or the target control file. 
C.A channel is a stream of data to a device type and corresponds to one server session. 
D.The RMAN executable interprets sever session commands and establishes connections to the target database.

A.A text copy of the control file.
B.A binary copy of the control file.
C.A file containing a SQL statement which will re-create the database.
D.A file containing a SQL statement which will re-create the control file.