Final answer:
Karen should use the SFC (System File Checker) command to examine and restore protected system files on a Windows system.
Step-by-step explanation:
The command that Karen, a technician, should use to examine and restore protected system files is SFC, which stands for System File Checker. This utility allows users to scan for corruption in Windows system files and restore them. The complete command to initiate this scan is sfc /scannow. It may require administrative privileges to run and can take some time to complete, depending on the system's configuration and the extent of file corruption.