Which type of backup backs up only data blocks modified since the most recent backup at the same level or lower?（）

A.All datafiles of a database 
B.All datafiles, archive logs, and control files 
C.All datafiles and control files 
D.All the used blocks in a datafile

A.With alter database enable block change tracking
B.With alter system enable block change tracking 
C.With an init.ora parameter change 
D.With an spfile parameter change 

A.Restore and recover the datafile. 
B.Restore and recover the tablespace. 
C.Restore and recover the database. 
D.Restore and recover the control file. 
E.Restore and recover the parameter file.