oracle ocp 19c考题，科目082考试题(19)-set unused column

19、choose the best answer Evaluate the following SQL statement:ALTER TABLE hr.empSET 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 be automatically modified and remain valid.B) Any constraints defined on the MGR_ID column would be removed by the above command.C) Any synonym existing on the EMP table would have to be re-created.D) Any index created on the MGR in column would continue to exist until the DROP UNUSED COLUMNS command is executed.source : cuug