The best way to verify the effectiveness of a data restoration process is to perform periodic complete data restorations. This is the process of transferring backup data to the primary system or data center and verifying that the restored data is accurate, complete, and functional. By performing periodic complete data restorations, the auditee can test the reliability and validity of the backup data, the functionality and performance of the restoration tools and procedures, and the compatibility and integrity of the restored data with the primary system. This will also help identify and resolve any issues or errors that may occur during the restoration process, such as corrupted or missing files, incompatible formats, or configuration problems.

Performing periodic reviews of physical access to backup media (option A) is not the best way to verify the effectiveness of a data restoration process, as it only ensures the security and availability of the backup media, not the quality or usability of the backup data. Physical access reviews are important for preventing unauthorized access, theft, damage, or loss of backup media, but they do not test the actual restoration process or verify that the backup data can be successfully restored.

Validating offline backups using software utilities (option C) is also not the best way to verify the effectiveness of a data restoration process, as it only checks the integrity and consistency of the backup data, not the functionality or compatibility of the restored data. Software utilities can help detect and correct any errors or inconsistencies in the backup data, such as checksum errors, duplicate files, or incomplete backups, but they do not test the actual restoration process or verify that the restored data can work with the primary system.

Reviewing and updating data restoration policies annually (option D) is also not the best way to verify the effectiveness of a data restoration process, as it only ensures that the policies are current and relevant, not that they are implemented and followed. Data restoration policies are important for defining roles and responsibilities, objectives and scope, standards and procedures, and metrics and reporting for the restoration process, but they do not test the actual restoration process or verify that it meets the expected outcomes.

Therefore, option B is the correct answer.