Concept:Controlling is the management function that checks actual performance and corrects deviations.
Explanation:Controlling begins by setting clear performance standards.
Actual outcomes are then compared with these standards.
When a gap or error is found, corrective action is taken to reduce it.
This ensures the organisation stays on track toward its goals.
Staffing, organizing, and directing do not focus mainly on measuring outcomes and correcting errors.
Therefore, the correct management function described is controlling.
Answer:D. controlling