What are the states of VNX Replicator replicas during normal operation and during failover?

A.
During normal operation, replicas are in Read Only mode. During Failover, replicas are in Read
Write mode.

B.
Replicas are always in Read Only mode. During Failover replicas serve as sources for recovery
processes.

C.
Replicas are in Read/Write modes except during Faiback mode when the replica becomes Gold
Copy and is in Read Only mode.

D.
Replicas are always in Read/Write mode but the Checkpoints protecting replicas are in Read
Only mode.