You are experiencing problems during the installation of Windows Server $2019.$ More specifically, critical file extensions have lost their associated program data. You need to restore the settings from a Registry backup.

Where will the settings be found?

a$.$ HKEY$\_$CLASSES$\_$ROOT

b$.$ HKEY$\_$LOCAL$\_$MACHINE

c$.$ HKEY$\_$CURRENT$\_$USER

d$.$ HKEY$\_$CURRENT$\_$CONFIG