Which of these statements is correct regarding SSO and Cisco NSF?（）

• A、Utilizing Cisco NSF in Layer 2 environments can reduce outages to one to three seconds.
• B、Utilizing SSO in Layer 3 environments can reduce outages to one to three seconds.
• C、Distribution switches are single points of failure causing outages for the end devices.
• D、Utilizing Cisco NSF and SSO in a Layer 2 environment can reduce outages to less than one second.
• E、NSF and SSO with redundant supervisors have the most impact on outages at the access layer.