单项选择题 You find this query being used in your Oracle 12c database: Which method a used by the optimizer to limit the rows being returned?（）

多项选择题 You performed an incremental level 0 backup of a database: RMAN > BACKUP INCREMENTAL LEVEL 0 DATABASE; To enable block change tracking after the incremental level 0 backup, you issued this command: SQL > ALTER DATABASE ENABLE BLOCK CHANGE TRACKING USING FILE ‘ /mydir/rman_change_track.f’; To perform an incremental level 1 cumulative backup, you issued this command: RMAN> BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE; Which three statements are true?（）

多项选择题 Your multitenant container database (CDB) contains some pluggable databases (PDBs), you execute the following command in the root container: Which two statements are true?（）