What must be configured between both cloud providers' authentication mechanisms?

What must be configured between both cloud providers’ authentication mechanisms?

A cloud architect is designing a hybrid cloud for an organization. A requirement for this environment is for federated access to both cloud provisioning APIs.

What must be configured between both cloud providers’ authentication mechanisms?
A . Shared super-user account
B . Trust relationship
C . Identical accounts
D . IPsec VPN

Answer: B