The best way to mitigate the ongoing risk associated with operating system (OS) vulnerabilities is to document and implement a patching process. A patching process is a set of procedures and guidelines that define how to identify, evaluate, test, apply, and monitor patches for the OS. Patches are updates or fixes that address the known vulnerabilities or bugs in the OS. By documenting and implementing a patching process, the organization can ensure that the OS is regularly updated and protected from the potential exploits or attacks that may exploit the vulnerabilities. The other options are not as effective as documenting and implementing a patching process, as they are related to the temporary, partial, or reactive measures to deal with the OS vulnerabilities, not the proactive and continuous measures to prevent or reduce the OS vulnerabilities. References = Risk and Information Systems Control Study Manual, Chapter 3: IT Risk Response, Section 3.3: IT Risk Response Implementation, page 145.