A unique index (IX1) currently exists on COL1, COL2 and COL3 of the table. There is a request to
be able to have an index on these three columns and COL4 to achieve the optimal access path.
The addition of COL4 will not support the uniqueness requirement of the index. In order to add this
column to the index while still preserving the unique constraint of the first three columns, which
option should be taken?

A.
Add a new index on COL4.

B.
Perform a ALTER INDEX IX1 ADD COLUMN (COL4).

C.
Add a new UNIQUE index on COL1, COL2, COL3, COL4.

D.
Perform an ALTER INDEX IX1 ADD INCLUDE COLUMN (COL4).

Explanation: