A system has a critical need for network services on a small network with a limited number of hosts. System overhead is not a concern. Which of the following should the system administrator do to help ensure connectivity in the event of a gateway failure？（）
A、Use the ifconfig command to enable dead gate detection
B、Use the no command to set active dead gateway detection
C、Use the route command to set active dead gateway detection
D、Add the line active_dgd=1 to the /etc/gated.conf command and refresh the gated daemon
