单项选择题 Data file DF1 belongs to tablespace TS1.，and the database is in ARCHIVELOG mode. You did an incomplete recover in the following steps：   1. Take data file DF1 offline.  2. Copy a backup copy of DF1 into the current DF1 location.  3. Execute RECOVER DATAFILE UNTIL TIME sometime in the past.  4. Bring DF1 online.  5. Execute ALTER DATABASE OPEN RESETLOGS.   To guarantee that the database is recoverable in the future， what is the least amount of work needed？（）

单项选择题 Anindex-organizedtable（IOT）calledSPARSEhashadmanyrecordsdeleted.WhichcommandreorganizestheIOTsothattheemptyspaceisremoved，whileminimizingtheimpactforusers？（）

多项选择题 The CURSOR_SHARING parameter is set to SIMILAR at the instance level and you issue these SELECT statements in the order shown below：   SELECT * FROM employees WHERE department_id=50；  SELECT * FROM employees WHERE department_id=70； There is an index on the DEPARTMENT ID column of the 1，000，000 row EMPLOYEES table. Ninety percent of the employees are part of the DEPARTMENT_ID 50. In which two scenarios will Oracle9i share the corresponding cursors for the two statements？（）