Examine the description of the EMPLOY

Examine the description of the EMPLOYEES table: Which statement produces the number of different departments that have employees with last name Smith?（）

• ASELECT COUNT(*) FROM employees WHERE last_name='Smith';
• BSELECT COUNT(dept_id) FROM employees WHERE last_name='Smith';
• CSELECT DISTINCT(COUNT(dept_id)) FROM employees WHERE last_name='Smith';
• DSELECT COUNT(DISTINCT dept_id) FROM employees WHERE last_name='Smith';
• ESELECT UNIQUE(dept_id) FROM employees WHERE last_name='Smith'