Which procedure should be used to configure the system to prevent all users from using the ’at’ command（）？  

• A、Create a /var/adm/cron/at.allow file with no entries
• B、Create a /var/adm/cron/at.deny file with ’*’ as the only entry
• C、Create a /var/adm/at/at.deny file with ’ALL’ as the only entry
• D、Create a /var/adm/at/at.allow file with ’NONE’ as the only entry