The primary benefit of configuring replica mapping in Veeam Backup & Replication is C: Reduced WAN traffic. Replica mapping is a feature that allows an administrator to map an existing VM in the disaster recovery site to a replica job. This is particularly useful when the initial replication of a large VM has been performed by other means (such as shipping a hard drive with the VM data to the DR site) or if a replica VM already exists and needs to be re-synced with the source VM. By using replica mapping, Veeam can avoid transferring the entire VM over the WAN again and instead only synchronize the differences between the source VM and the existing replica. This significantly reduces the amount of data that needs to be transferred over the WAN, conserving bandwidth and speeding up the replication process. It's an efficient way to manage replicas, especially for large VMs or in environments with limited bandwidth.