Identify two correct statements about multitenant architectures.（）

• A、Multitenant architecture can be deployed only in a Real Application Clusters (RAC) configuration.
• B、Multiple pluggable databases (PDBs) share certain multitenant container database (CDB) resources.
• C、Multiple CDBs share certain PDB resources.
• D、Multiple non-RAC CDB instances can mount the same PDB as long as they are on the same server.
• E、Patches are always applied at the CDB level.
• F、A PDB can have a private undo tablespace.