Which two statements are true about the UNDROP clause of the ALTER DISKGROUP statement? 

Answer options:

A. It cancels pending drops of disks dropped using the DROP DISKGROUP command.
B. A disk cannot be undropped as a result of a drop diskgroup.
C. It automatically unmounts the disks after successfully undropping them.
D. It is not possible to cancel pending drops of disks dropped using the force option.

BD

The UNDROP DISKS clause of the ALTER DISKGROUP statement cannot be used to restore disks that are being dropped as the result of a DROP DISKGROUP statement, or for disks that are being dropped using the FORCE clause. Reference: https://docs.oracle.com/cd/B28359_01/server.111/b31107/asmdiskgrps.htm