Examine the description of the EMPLOYEES table: EMP_ID NUMBER(4) NOT NULL LAST_NAME VARCHAR2(30) NOT NULL FIRST_NAME VARCHAR2(30) DEPT_ID NUMBER(2) Which statement produces the number of different departments that have employees with last name Smith?（）

• A、SELECT COUNT (*) FROM employees WHERE last _name='smith';
• B、SELECT COUNT (dept_id) FROM employees WHERE last _name='smith';
• C、SELECT DISTINCT (COUNT (dept_id) FROM employees WHERE last _name='smith';
• D、SELECT COUNT (DISTINCT dept_id) FROM employees WHERE last _name='smith';
• E、SELECT UNIQE (dept_id) FROM employees WHERE last _name='smith';