Explanation
The BEST indication that an organization's vulnerability management process is operating effectively is that remediation efforts are prioritized. This is because prioritizing remediation efforts helps to ensure that the most critical and urgent vulnerabilities are addressed first, based on their severity, impact, and exploitability.
Prioritizing remediation efforts also helps to optimize the use of resources and time for mitigating vulnerabilities and reducing risks. The other options are not as indicative of an effective vulnerability management process, because they either involve communicating (A), approving (B), or reviewing C aspects that are not directly related to remediating vulnerabilities.