Final answer:
The correct statement about a substantive approach in auditing is that auditors may test the effectiveness of internal control if it is in place. Other options contain misunderstandings about how the level of internal control influences the auditors' assessment of risk and their testing approach.
Step-by-step explanation:
The correct statement regarding a substantive approach in auditing is 4) If there is an internal control in place, auditors may decide to test the effectiveness of the internal control. In auditing, the Risk of Material Misstatement (RMM) involves assessing both the inherent and control risks. A substantive approach often involves a high level of detailed testing of account balances and transactions when the auditor has determined that internal controls are weak and cannot be relied upon, contrary to what is suggested in statement 2). Statement 3) is incorrect as both approaches start similarly, with planning and risk assessment. In contrast, statement 1) is incorrect because a lack of internal control would typically increase the assessed RMM, not lower it.