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.