Final answer:
When using MBO, a manager must set clear objectives.
Step-by-step explanation:
When using MBO (Management by Objectives), a manager must set clear objectives. MBO is a goal-setting approach where managers work with their employees to set specific, measurable, achievable, relevant, and time-bound (SMART) objectives. By setting clear objectives, managers provide a roadmap for their employees and align their efforts with the overall organizational goals.