The status of your ZFS file system is as follows:
raidz FAULTED
c1t0d0 ONLINE
c2t0d0 FAULTED
c3t0d0 FAULTED
c4t0d0 ONLINE
Which answer describes the condition of your file system?

A.
Neither disk can be replaced because not enough healthy replicas from which to retrieve data exist.

B.
Replace both drives and any data in the pool is copied to the replaced drives. Healthy replicas exist on c1t1d0 and c4t0d0.

C.
Neither disk can be replaced. Although enough healthy replicas exist, too much data has been lost to recover the data in the file system.

D.
Replace c2t0d0 first, when it is ONLINE and data has been copied from c1t0d0, replace disk c3t0d0. Wait for the pool to come back ONLINE.