A significant number of Qualitex Corporation' s department heads are due to retire this year. The number of employees other than current department heads who could take on the position of department head is equal to only about half of the expected vacancies. Oualitex is not going to hire department heads from outside the company or have current department heads take over more than one department, so some departments will be without department heads next year unless Qualitex __. Which of the following most logically completes the argument? ['reduces the average number of employees per department', 'reduces the number of its departments', 'raises the salary for department heads', 'promotes some current department heads to higher-level managerial positions']