Final answer:
The action by the nurse manager that demonstrates the function of directing is developing a staffing schedule.
Step-by-step explanation:
The action by the nurse manager that demonstrates the function of directing is A. Developing a staffing schedule. Directing is one of the functions of management that involves guiding and overseeing the activities of employees to achieve organizational goals. By developing a staffing schedule, the nurse manager is providing direction for the staff, ensuring that there is adequate coverage and coordination of work.