What is the correct order of the following commands if you wanted to restore datafile 4， which was accidentally removed from the file system？（）   a. sql ’alter database datafile 4 online’ b. restore datafile 4 c. recover datafile 4  d. sql ’alter database datafile 4 offline’ e. startup  f. shutdown

• A、 a， c， b， d
• B、 d， b， c， a
• C、 f， d， b， c， a， e
• D、 c， a， b， d， f
• E、 a， b， d， e