The BEST feature that facilitates the development of metrics for reporting to senior management on vulnerability management efforts is tracking vulnerabilities and the remediation efforts to mitigate them. This is because tracking vulnerabilities and remediation efforts helps to measure and monitor the performance and effectiveness of vulnerability management efforts, by providing quantifiable and objective data on the number, severity, impact, status, and resolution time of vulnerabilities. Tracking vulnerabilities and remediation efforts also helps to identify and communicate any gaps or issues in vulnerability management efforts to senior management and other stakeholders. The other options are not features that facilitate the development of metrics for reporting to senior management on vulnerability management efforts, but rather different aspects or factors that affect vulnerability management efforts, such as reviewing business impact analysis (BIA) results (A), benchmarking with industry peers (B), or monitoring the frequency of vulnerability assessments (D).