Evaluate the following SQL statement: ALTER TABLE hr.emp SET UNUSED (mgr_id);
Which statement is true regarding the effect of the above SQL statement?
A.
 Any views created on the EMP table that include the MGR_ID column would have to be 
dropped and re-created.
B.
 Any index created on the MGR_ID column would continue to exist until the DROP 
UNUSED COLUMNS command is executed.
C.
 Any synonym existing on the EMP table would have to be re-created.
D.
 Any constraints defined on the MGR_ID column would be removed by the above 
command.