Which two statements are true about a bitmap index? (Choose two.)
A.
It is recommended for the columns that have unique values.
B.
It can be converted to a B-tree index by using the ALTER INDEX command.
C.
It has a bitmap segment for each distinct value in the key column, containing a string of bits in which each bit represents the presence or absence of a key column value.
D.
Updating the key column locks the whole bitmap segment that contains the bit for the key value to be updated.