Root login should only be allowed via:

A.
Rsh

B.
System console

C.
Remote program

D.
VNC

Explanation:
The root account must be the only account with a user ID of 0 (zero) that has open
access to the UNIX shell. It must not be possible for root to sign on directly except
at the system console. All other access to the root account must be via the ‘su’
command.