Which two aspects can be determined from this output?

This MDADM output:

Which two aspects can be determined from this output?

A.
A device failed and has been removed from this RAID set.

B.
It is no longer possible to write to this RAID set.

C.
Read and write performance is no longer optimal on this RAID set.

D.
This RAID set was built without a spare device.

E.
Only Write performance is no longer optimal on this RAID set.

Explanation: