What is required to implement Auto Image Replication?

What is required to implement Auto Image Replication?
A . BasicDisk or AdvancedDisk storage units and at least one Master Server
B. OST-compliant appliances or MSDP and at least one Master Server
C. OST-compliant appliances or MSDP and at least two Master Servers
D. BasicDisk or AdvancedDisk storage units and at least two Master Servers

Answer: C