Which two statements regarding the LOGGING clause of the CREATE TABLESPACE. .. statement are correct？（）

• A、This clause is not valid for a temporary or undo tablespace.
• B、If the tablespace is in the NOLOGGING mode， no operation on the tablespace will generate redo.
• C、The tablespace will be in the NOLOGGING mode by default， if not specified while creating a tablespace.
• D、The tablespace­level logging attribute can be overridden by logging specifications at the table， index， materialized view， materialized view log， and partition levels.