What is one of the features of deploying Cisco Unified Communications Manager servers in a 1:1 redundancy design?

A.
When the primary servers approach 100% utilization, the backup servers can take over a portion of the load

B.
If a single primary server fails, multiple servers can distribute the load generated by users reregistering from the failed server.
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Cisco 642-447 Exam

C.
If multiple servers fail concurrently, the resulting load generated by users reregistering does not overwhelm the dedicated backup servers

D.
Recovery happens faster when the load generated by the users from a failed server is spread over more than one backup server

Explanation:
Incorrect answer : ABD
Link : http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/8x/callpros.html#wp1151374 Reference : Cisco Unified Communications System Release 8.x SRND , page- 283. Explanation : One to one (1:1) — For every primary call processing subscriber, there is a secondary or backup call processing subscriber.