What of the following statements is true regarding a display manager?
A. A display manager handles remote X11 logins only and has no purpose on a system that is not attached to a network.
B. The display manager is configured in the X11 configuration file xorg.conf.
C. There is only one display manager X11DM that must be started on all systems running X11.
D. After system startup, the display manager handles the login of a user.
E. Without a display manager, no graphical programs can be run.