Which system memory metrics are measured regarding total memory?

B is the most applicable choice when discussing system memory metrics related to total memory. The total memory measurement encompasses several important components, which include free memory (memory that is currently unused and available for allocation), and reclaimable memory (memory that can be freed up or returned to the system if needed). By focusing on these metrics, one can understand not only how much memory is currently in use but also how much is freely available for new processes or tasks.

This perspective is crucial when assessing system performance and ensuring optimal resource allocation. Metrics like free and reclaimable help administrators identify potential memory bottlenecks or saturation points in a system, paving the way for better optimization strategies.