Final answer:
Tests of controls are audit procedures used to evaluate the effectiveness of internal controls; while reperformance, observation, and inspection are part of these tests, inquiries of client vendors are typically not.
Step-by-step explanation:
Tests of controls are procedures auditors use to test the effectiveness of a company's internal controls. These tests are least likely to include inquiries of appropriate client vendors, as this option relates more to substantive testing rather than testing the control process itself. The other options, reperformance of a control, observation of the application of an accounting procedure, and inspection of documents, are all direct methods auditors use to assess the functioning and effectiveness of internal controls. These are designed to ensure that the controls in place are being applied consistently and are adequate in preventing or detecting errors or fraud.
Tests of controls include reperformance, where the auditor independently executes the procedures to verify their effectiveness. Observation includes watching the application of a specific process or procedure. Inspection involves the examination of documents to ensure the control has been applied properly. However, inquiries of client vendors are more aligned with collecting evidence on the actual outcomes or transactions rather than the processes.