What are two considerations when using SSO as a network redundancy feature? (Choose two.)

What are two considerations when using SSO as a network redundancy feature? (Choose two.)
A . must be combined with NSF to support uninterrupted Layer 2 operations
B . must be combined with NSF to support uninterrupted Layer 3 operations
C . both supervisors must be configured separately
D . the multicast state is preserved during switchover
E . requires synchronization between supervisors in order to guarantee continuous connectivity

Answer: B E