The answer D is correct because the best way for the auditor to confirm the change log is complete is to take the last change from the system and trace it back to the log. A change log is a record of all the changes that have been made to a system, such as software updates, bug fixes, configuration modifications, etc. A change log should contain information such as the date and time of the change, the description and purpose of the change, the person or service who made the change, and the approval status of the change. A complete change log helps to ensure that the system is secure, reliable, and compliant with the relevant standards and regulations.

An IS auditor evaluating the change management process must select a sample from the change log to verify that the changes are properly authorized, documented, tested, and implemented. However, before selecting a sample, the auditor must ensure that the change log is complete and accurate, meaning that it contains all the changes that have been made to the system and that there are no missing, duplicated, or falsified entries. To do this, the auditor can use a technique called backward tracing, which involves taking the last change from the system and tracing it back to the log. This way, the auditor can check if the change is recorded in the log with all the relevant details and if there are any gaps or inconsistencies in the log. If the last change from the system is not found in the log or does not match with the log entry, it indicates that the change log is incomplete or inaccurate.

The other options are not as good as option D. Interviewing change management personnel about completeness (option A) is not a reliable way to confirm the change log is complete because it relies on subjective opinions and self-reported information, which may not be truthful or accurate. Taking an item from the log and tracing it back to the system (option B) is a technique called forward tracing, which can be used to verify that a specific change in the log has been implemented in the system. However, this technique does not confirm that all changes in the system are recorded in the log. Obtaining management attestation of completeness (option C) is not a sufficient way to confirm the change log is complete because it does not provide any evidence or verification of completeness. Management attestation may also be biased or influenced by conflicts of interest.