Which of the following activities would be most appropriate for mitigating the risk of releasing...

Regression testing is crucial when releasing patches as it ensures that the new changes have not adversely affected the existing functionality of the software. It involves re-running previous tests on the modified software to confirm that the old functionalities still work as expected and that the new patches do not introduce new defects.

Partial releases, software rebuilds, and configuration management are important aspects of software maintenance, but regression testing directly addresses the risk of introducing new issues with patches.

References:

"Software Testing: Principles and Practices" by Naresh Chauhan.

IEEE Standard 829-2008 for Software and System Test Documentation.