Which statement is true concerning dropping a pluggable database (PDB)?
A. The PDB must be open in read-only mode.
B. The PDB must be in mount state.
C. The PDB must be unplugged.
D. The PDB data files are always removed from disk.
E. A dropped PDB can never be plugged back into a multitenant container database (CDB).
BC is correct
https://docs.oracle.com/database/121/ADMIN/cdb_plug.htm#ADMIN13658
The PDB must be in mounted mode, or it must be unplugged.
BD is correct
https://docs.oracle.com/database/121/ADMIN/cdb_plug.htm#ADMIN13658
The PDB must be in mounted mode, or it must be unplugged.