Which of the following two statements about Cisco NSF and SSO are the most relevant to the network designer? (Choose two.)

A.
You can reduce outages to 1 to 3 seconds by using SSO in a Layer 2 environment or Cisco NSF with SSO in a Layer 3 environment.

B.
SSO and NSF each require the devices to either be graceful restart-capable or graceful restart-aware.

C.
In a fully redundant topology adding redundant supervisors with NSF and SSO may cause longer convergence times than single supervisors with tuned IGP
timers

D.
The primary deployment scenario for Cisco NSF with SSO is in the Distribution and Core layers.

Explanation:
http://www.ciscopress.com/articles/article.asp?p=1315434
In a fully redundant topology with tuned IGP timers, adding redundant supervisors with Cisco NSF and SSO may cause longer convergence times than single
supervisors with tuned IGP timers. NSF attempts to maintain the flow of traffic through a router that has experienced a failure. NSF with SSO is designed to
maintain a link-up Layer 3 up state during a routing convergence event. However, because an interaction occurs between the IGP timers and the NSF timers, the
tuned IGP timers can cause NSF-aware neighbors to reset the neighbor relationships.
In nonredundant topologies, using Cisco NSF with SSO and redundant supervisors can provide significant resiliency improvements.
“A graceful restart-aware neighbor is required so that graceful restart -capable systems can rebuild their databases and maintain their neighbor adjacencies across
a switchover.”