单项选择题

A. By default cloned routes are turned on.  To turn cloned routes off issue the command:      #no -o tcp_pmtu_discover=0       #no -o udp_pmtu_discover=0       and add to the rc.net or rc.bsdnet file for next reboot
B. By default cloned routes are turned on.  To turn cloned routes off issue the command:        # no -o tcp_pmtu_discover=1        #no -o udp_pmtu_discover=1         and add to the rc.net or rc.bsdnet file for next reboot
C. By default cloned routes are turned on.  To turn cloned routes off issue the command:         #no -o ipforwarding=0         and add to the rc.net or rc.bsdnet file for next reboot
D. By default cloned routes are turned on.  To turn cloned routes off issue the command:         #no -o ipforwarding=1         and add to the rc.net or rc.bsdnet file for next reboot