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單項選擇題

Your database is set in NOARCHIVELOG mode and is backed up every night. There are 10 redo log groups on the database， each with three members， making a total of 30 redo log files. At lunchtime the server unexpectedly gets shut down. Upon restarting you notice that the data file belonging to the SYSTEM tablespace has become corrupted. You also notice that there have been 15 log switches during the day. Which solution should you use to recover as much committed data as possible？（）

A.Restore the data file for the SYSTEM tablespace then open the database. 
B.Restore all redo logs form last night's backup, then restart the database. 
C.Perform a complete restore of all files from last night's backup. Data entered into the database today must be reentered. 
D.Mount the instance, take the SYSTEM tablespace offline, open the database, and then restore the data file, recover it, and bring the tablespace online. 

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