Which Cisco Unified Communications Manager deployment model for clustering over the IP WAN mandates a primary and a backup subscriber at the same site? 

Answer options:

A. multisite with centralized call processing
B. multisite with distributed call processing
C. local failover
D. remote failover
E. remote failover with Cisco Unified Communications Manager Express as SRST

C

Clustering Over the IP WAN - You may deploy a single Unified CM cluster across multiple sites that are connected by an IP WAN with QoS features enabled. This section provides a brief overview of clustering over the WAN. For further information, refer to the chapter on Call Processing. Clustering over the WAN can support two types of deployments: Local Failover Deployment Model - Local failover requires that you place the Unified CM subscriber and backup servers at the same site, with no WAN between them. This type of deployment is ideal for two to four sites with Unified CM. Remote Failover Deployment Model Remote failover allows you to deploy primary and backup call processing servers split across the WAN. Using this type of deployment, you may have up to eight sites with Unified CM subscribers being backed up by Unified CM subscribers at another site. References: http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/4x/42models.html