Nonstop Forwarding works with the Stateful Switchover feature in Cisco IOS and IOS XR software. Which three restrictions for OSPF are true?

A.	OSPF NSF for virtual links is not supported.
B.	OSPF NSF for virtual links is supported.
C.	OSPF NSF for sham links is not supported.
D.	OSPF NSF for sham links is supported.
E.	OSPF NSF supports NSF/SSO for IPv6 traffic only.
F.	OSPF NSF supports NSF/SSO for IPv4 traffic only.