在SQL Server中，某表的department字段有以下值：
marketing, production, production, sales, NULL, NULL, Marketing, NULL
下面的查询会返回什么结果：( )
Select distinct(department) from employees
marketing, production, sales
marketing, production, sales, NULL
marketing, production, sales, NULL, NULL
marketing, production, sales, NULL, Marketing
marketing, production, sales, NULL, NULL, Marketing
