An administrator has just set up the X Display Manager as the default display manager. Which of the following files should be edited to change the default background for it?

The `/etc/X11/xdm/Xsetup` script is executed by `xdm` at server startup (before the login screen appears) on the console display. This script is the appropriate place to include commands, such as `xsetroot` or `xloadimage`, to set the background of the X display.

`/etc/X11/prefdm` is typically a script used to choose which display manager to run, not to configure its visual appearance or background.

`/etc/X11/xorg.conf` configures the X server itself (e.g., input devices, display resolution, drivers), not the visual appearance or background of the display manager.

`/etc/X11/xdm.conf` (or often `/etc/X11/xdm/xdm-config`) contains `xdm`'s main configuration directives, but the `Xsetup` script is where specific visual commands like background setting are placed.