Final answer:
The nurse manager should first explore how the planning committee evaluated barriers to the plan.
Step-by-step explanation:
In order to address the staff's complaints about changing staff assignments from 8 hour shifts to 12 hour shifts, the nurse manager should first B) Explore how the planning committee evaluated barriers to the plan. This will help identify any concerns or issues that were not properly considered during the planning process. By understanding these barriers, the nurse manager can then work on addressing them and finding possible solutions to alleviate the staff's concerns.