In which two instances should an administrator run the Manage Indexes Rebuild tool? (Select two.)

In which two instances should an administrator run the Manage Indexes Rebuild tool? (Select two.)
A . to rebuild index volumes after they have been upgraded to 64-bit
B . to rebuild index volumes that the Change Location tool has moved
C . to rebuild index volumes after their Indexing Level has been changed
D . to rebuild index volumes to clear the Failed status
E . to rebuild index volumes that the Synchronize tool has failed to fix

Answer: C,E