单项选择题
A. Backup RB1 at log sequence number 12871 on 5th Jan
B. Backup RB2 at log sequence number 15622 on 12th Jan
C. Backup RB3 at log sequence 16721 on 15th Jan
D. On 20th Jan when the log sequence number was 18112 you realize that there Is a need to a point in time at the beginning of the recovery window. You have all an hived redo log files to date.