Final answer:
After the review and evaluation phase of an audit, the auditor should perform tests of controls on the internal control system to assess their effectiveness.
Step-by-step explanation:
After finishing the review phase of the study and evaluation of internal control in an audit, the auditor should perform tests of controls on the internal control system. This is because the internal control system is designed to ensure the accuracy and reliability of the financial statements and adherence to applicable laws and regulations. Testing the controls allows the auditor to assess the effectiveness of these controls in practice, which is essential for forming an opinion on the state of the company's financial health.