Examine the description of the EMPLOYEES table:<br /> <img src="https://nimg.ppkao.com/2018-08/zhangxu/2018080110341576486.jpg?sign=733550364557e2fe22444b81b3c2c6e4&t=62d02af7" style="width: 338px; height: 71px;" /><br /> 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 UNIQUE(dept_id) FROM employees WHERE last_name='Smith';