Which two statements are true about dropping a pluggable database (PDB)? 

Answer options:

A. A PDB must be in mount state or it must be unplugged.
B. The data files associated with a PDB are automatically removed from disk.
C. A dropped and unplugged PDB can be plugged back into the same multitenant container database (CDB) or other CDBs.
D. A PDB must be in closed state.
E. The backups associated with a PDB are removed.
F. A PDB must have been opened at least once after creation.

AD

Reference: http://docs.oracle.com/database/121/ADMIN/cdb_plug.htm#ADMIN13858