What is unique about the Quality of Service (QoS) function within IBM DS8000 as compared to other IBM storage products?

What is unique about the Quality of Service (QoS) function within IBM DS8000 as compared to other IBM storage products?
A . I/O Priority Manager can be integrated with the System z WLM
B . I/O Priority Manager is only supported for z Systems
C . The IBM DS8000 is the only IBM storage system offering QoS
D . System z and Open/distributed volumes can use the same managed Performance Groups

Answer: B