Final answer:
To troubleshoot a video issue, the DirectX Diagnostic Tool (Dxdiag) should be used, as it provides detailed information and testing options for video-related hardware problems.
Step-by-step explanation:
When troubleshooting a video issue on a computer, the most appropriate utility to use among the options provided is C. Dxdiag. DirectX Diagnostic Tool (dxdiag) is a diagnostic tool used to test DirectX functionality and troubleshoot video- or sound-related hardware problems. Running dxdiag allows you to view information specific to your video card and driver, as well as perform various tests on your system's DirectDraw, Direct3D, and DirectSound capabilities.
Other mentioned utilities like Regedit (Registry Editor) are for more advanced users wanting to edit system registry and are not specifically designed for troubleshooting video issues. Msconfig (System Configuration) can be used to modify startup programs and services, which is helpful for performance issues but not typically for direct video troubleshooting. Task Manager can show currently running programs and system performance but does not provide detailed diagnostic information regarding video hardware or drivers.