What is the purpose of the xhost program?
A. Grant or revoke access to a X11 session.
B. Install all packages and video drivers required to run X11 on a host.
C. Start the X11 server and announce its availability within the local network.
D. Send informational messages to all users logged into a host using X11.
E. Display the MOTD and other important information when a user logs in via X11.