Which substitution variable would you use if you want to reuse the variable without prompting the user each time?（）

A.It allows a grantee DBA privileges.
B.It is required syntax for object privileges.
C.It allows privileges on specified columns of tables.
D.It is used to grant an object privilege on a foreign key column.
E.It allows the grantee to grant object privileges to other users and roles.

A. SELECT ENAME   FROM EMP   WHERE SYSDATE-HIRE_DATE > 5;
B. SELECT ENAME   FROM EMP   WHERE HIRE_DATE-SYSDATE > 5;
C. SELECT ENAME   FROM EMP   WHERE (SYSDATE-HIRE_DATE)/365 > 5;
D. SELECT ENAME   FROM EMP   WHERE (SYSDATE-HIRE_DATE)* 365 > 5;

A.UNIQUE
B.NOT NULL
C.CHECK
D.PRIMARY KEY
E.FOREIGN KEY