The correct answer is A. Install the latest graphics drivers.
The most likely cause of the external monitor not working after an operating system upgrade is that the graphics drivers are incompatible with the new version. Installing the latest graphics drivers from the manufacturer's website or using Windows Update can resolve this issue. Replacing the monitor, restoring the operating system to the previous version, or reseating the external video adapter are not effective solutions for this problem.
References: You can find more information about troubleshooting external monitor connections in Windows
101 and Windows 112. You can also learn how to update the display driver using Device Manager2.