Why does the above statement return no rows selected as the result? Mr. King is the president of a company. Five managers report to him. All other employees report to these managers. Examine the code: SELECT employee.ename FROM emp employee WHERE employee.empno NOT IN (SELECT manager.mgr FROM emp manager);
A. NOT IN operator is not allowed in subqueries. B. All employees have a manager. C. None of the employees has a manager. D. A NULL value is returned from the subquery.