Which three statements are true concerning the multitenant architecture?（）

• A、Each pluggable database (PDB) has its own set of background processes.
• B、A PDB can have a private temp tablespace.
• C、PDBs can share the sysaux tablespace.
• D、Log switches occur only at the multitenant container database (CDB) level.
• E、Different PDBs can have different default block sizes.
• F、PDBs share a common system tablespace.
• G、Instance recovery is always performed at the CDB level.