Final answer:
The least likely test of a control is the inspection of management's engagement letter because it does not assess control effectiveness but rather the agreement terms with management.
Step-by-step explanation:
The item least likely to be a test of a control is b. Inspection of management's engagement letter. A test of a control is used to verify the effectiveness of an internal control designed to prevent or detect errors and fraud. While inquiries of appropriate personnel, observation of the application of a policy, and reperformance of the application of a policy are all methods to test if the controls are functioning as intended, the inspection of management's engagement letter would not typically serve as a method to assess the operational effectiveness of internal controls. It might, instead, provide information about the terms and responsibilities agreed upon with management.