Cat6500（config）# router ospf 1  Cat6500（config-router）# network 0.0.0.0 255.255.255.255 area 0  Cat6500（config-router）# nsf Cat6500（config-router）#end  Refer to the exhibit. The configuration is used to enable nonstop forwarding for OSPF on a Catalyst 6500 Series  Switch with redundant supervisor engines.  The default CEF configuration is unchanged. After testing， user traffic is interrupted and NSF is not operational.  What is the most likely reason？ （）

• A、CEF was not properly configured.
• B、OSPF was not properly configured for graceful restart.
• C、Stateful switchover was not correctly configured.
• D、NSF for OSPF is only supported in area 0.