Which statement best describes Cisco supervisor engine redundancy using Stateful Switchover?

Which statement best describes Cisco supervisor engine redundancy using Stateful Switchover?

A.
Switchover ensures that Layer 2 through Layer 4 traffic is not interrupted.

B.
Redundancy requires BGP, OSPF, EIGRP, or IS-IS.

C.
Redundancy provides fast supervisor switchover for all Cisco Catalyst 6500 series switches.

D.
Switchover can be caused by clock synchronization failure between supervisors.