A PC is running slower than usual. Which of the following tools would BEST diagnose the possible bottleneck?

CHKDSK scans for file system corruption and bad sectors; it reports disk integrity issues but does not display real-time performance metrics or identify active bottlenecks.

Device Manager shows hardware devices and their driver status and is used to diagnose driver conflicts, not runtime performance bottlenecks.

Task Scheduler manages automated tasks and their schedules and has no functionality for monitoring or diagnosing live system performance.

Task Manager displays live resource usage for all running processes, including per-process CPU percentage, memory consumption, disk I/O, and network activity. A technician can immediately identify which process or resource is saturated - for example, 100% CPU usage by a specific application or maximum disk utilization - and pinpoint the bottleneck causing the slowdown. The Performance tab also provides historical graphs to confirm sustained resource contention.